Media playback is unsupported on your device Media caption Richard Westcott reports on the ongoing investigation into the crash 
 
 The Russian airline Kogalymavia has blamed "external influence" for Saturday's Sinai plane crash which killed 224 people. 
 
 A senior airline official said: "The only reasonable explanation is that it was [due to] external influence." 
 
 An investigation by aviation experts using data from the aircraft's "black boxes" has yet to give its conclusions. 
 
 The head of Russia's Federal Aviation Agency said it was premature to speculate on the cause of the crash. 
 
 "This kind of talk is... not based on any proper facts," Aleksandr Neradko said on Russian TV. 
 
 Egyptian President Abdel Fattah el-Sisi also said in an interview with the BBC that it was too early to say what had caused the crash. 
 
 He called a claim from jihadis allied to the so-called Islamic State (IS) group that they had brought down the plane "propaganda". 
 
 "This is one way to damage the stability and security of Egypt and the image of Egypt," he said. 
 
 Media playback is unsupported on your device Media caption President Sisi said the area of Sinai concerned was "under our full control" 
 
 James Clapper, the US director of national intelligence, said there was no "direct evidence of any terrorist involvement yet" adding: "It's unlikely, but I wouldn't rule it out." 
 
 Russian President Vladimir Putin has described the crash as an "enormous tragedy" and expressed his condolences to the families of the victims. 
 
 "Without any doubt, everything must be done to create an objective picture of events so that we know what happened and can react accordingly," he said. 
 
 At a news conference in Moscow, the deputy director of the airline, which was later renamed Metrojet, ruled out a technical fault and pilot error. 
 
 "The only [explanation] for the plane to have been destroyed in mid-air can be specific impact, purely mechanical, physical influence on the aircraft," Alexander Smirnov said. 
 
 "There is no such combination of failures of systems which could have led to the plane disintegrating in the air," he added. 
 
 Another airline official acknowledged that there had been previous damage to the plane's tail in 2001 during take-off. 
 
 But he said that the damage had been repaired, and was not thought to be a factor in the crash. 
 
 However, the widow of the plane's co-pilot told Russian TV her husband had complained about the aircraft's technical condition. 
 
 Media playback is unsupported on your device Media caption Sarah Rainsford reports from a morgue in St Petersburg where bodies are being identified 
 
 The Airbus 321 lost speed and started descending rapidly, and the crew made no attempt to get in contact and report about the situation on board, Mr Smirnov added. 
 
 The bodies of 144 of those killed in the crash have been flown back to the Russian city of St Petersburg, where the plane had been headed from the Egyptian resort of Sharm el-Sheikh. 
 
 Russian Emergency Situations Minister Vladimir Puchkov said that searches in a 20-sq-km (7.7-sq-Mile) area around the crash site had ended and that a 30-sq-km area was now being searched. 
 
 Mr Puchkov said searches would not end until all the bodies have been recovered, AP reports. 
 
 The plane was carrying 217 passengers, including 25 children, and seven crew members - mostly Russians. 
 
 Timeline: the course of flight KGL9268 
 
 05:58 Egyptian time (03:58 GMT): Flight leaves Sharm el-Sheikh, a statement from the Egyptian cabinet says 
 
 06:14 Egyptian time (04:14 GMT): Plane fails to make scheduled contact with air traffic control based in Larnaca, Cyprus, according to Sergei Izdolsky, an official with Russia's air transport agency 
 
 06:17 Egyptian time, approx (04:17 GMT): Plane comes down over the Sinai peninsula, according to Airbus 
 
 11:12 Egyptian time (09:12 GMT): Flight had been due to land in St Petersburg's Pulkovo airport ||||| Here’s what we know about the deadly crash of a Russian airliner in Egypt that killed all 224 people on board Saturday. (Monica Akhtar/The Washington Post) 
 
 Here’s what we know about the deadly crash of a Russian airliner in Egypt that killed all 224 people on board Saturday. (Monica Akhtar/The Washington Post) 
 
 A public quarrel erupted Monday over the cause of the weekend plane crash in Egypt that killed 224 people, and it pitted the airline that operated the Airbus jet against the Russian government. 
 
 Metrojet, a small Russian airline scrambling to protect its reputation after the devastating crash, found itself at odds with government officials who wanted to contain speculation about what led to the deadliest civil aviation disaster in Russia’s history. 
 
 [Sinai increasingly restive and unstable] 
 
 When a senior Metrojet official declared Monday that the company had ruled out pilot error or a technical malfunction as the reason for the crash, the government responded with a swift rebuke. 
 
 “That statement is premature and is based on no real facts,” Alexander Neradko, the head of Russia’s Federal Air Transport Agency, said in a television interview from Egypt. 
 
 Investigators have not said whether a technical malfunction, pilot error or an act of terrorism caused the Airbus A321-200 to disintegrate over Egypt’s troubled Sinai Peninsula on Saturday, scattering debris over seven square miles of desert. Investigators have retrieved the plane’s black boxes but have not reviewed them yet, Neradko said in the interview. 
 
 “Yes, we know that components of the plane have been thrown over a wide area. That says that the breakup took place in the air, at a high altitude,” he said. “But it is very premature to talk about the reasons. I would like to call on the aviation community to abstain from premature statements.” 
 
 While an Egyptian affiliate of the Islamic State seized the opportunity to claim responsibility for the plane crash Saturday, Russian officials remained skeptical. 
 
 The claim led some international carriers to reroute flights away from the Sinai, though defense experts have raised strong doubts about whether the Islamic State could have missile systems capable of hitting an airliner at 31,000 feet. 
 
 In Washington, James R. Clapper Jr., the director of national intelligence, said that there was no “direct evidence of terrorist involvement yet” but that it cannot be disregarded. “It’s unlikely, but I wouldn’t rule it out,” Clapper told reporters. 
 
 Prevailing wisdom holds that once an airplane reaches cruising altitude, it’s clear sailing, but there have been at least half a dozen times when a commercial jetliner has fallen to pieces without help from a bomb or a missile. 
 
 [What would cause a plane to break up in midair?] 
 
 : Russia mourns after airliner crashes in Egypt: None of the 224 people on board a Russian aircraft survived after it went down en route from an Egyptian resort area to St. Petersburg. ( / ) 
 
 What happened to the Metrojet flight is a riddle whose answer is fraught with consequences, either implicating Russia’s troubled airline industry or suggesting that Russia was targeted by terrorists, possibly because of the country’s intervention in Syria’s civil war. 
 
 “On the one hand, saying that it was ISIS might be convenient from the point of view that it’s not actually lax maintenance and safety standards” that caused the crash, said Alex Kazbegi, a transport analyst at Renaissance Capital, using an acronym for the Islamic State. 
 
 “But on the other hand, saying it was ISIS could be saying it was actually a response to Russia being in Syria, which may also be considered politically unacceptable.” 
 
 Russian President Vladi­mir Putin called the accident “a great tragedy” Monday. 
 
 “Everything must be done to create an objective picture of what happened so that we know what happened and react accordingly,” Putin told Transport Minister Maxim Sokolov during a televised briefing on the investigation. 
 
 As the investigation continues, there are unmistakable signs that Metrojet is in the crosshairs. 
 
 Investigators this weekend opened a probe for criminal negligence in the crash and searched Metrojet’s offices. Russia’s Federal Labor Agency announced Monday that the airline had not paid its employees in the past two months, indicating financial problems in the company. And a state-owned television channel broadcast an interview with the pilot’s wife, who said her husband had complained about poor maintenance on the plane. 
 
 Metrojet’s embattled leadership mounted a public defense Monday at a news conference in Moscow. 
 
 Alexander Smirnov, the deputy general director of the airline, said no combination of factors, including bad fuel or engine failure, could have led the plane to break up in midair. Metrojet officials also said that the plane was regularly reviewed for signs of structural weakening and argued that although the company had withheld wages recently, that did not affect safety standards. 
 
 “The only explanation could be a mechanical impact on the aircraft,” Smirnov said. He declined to elaborate as to what such an impact could have been. 
 
 Though Smirnov discounted the possibility that the Metrojet plane could have fatally malfunctioned, it would not be unprecedented. 
 
 [Egypt’s upheaval has transformed much of the Sinai into a no-go zone] 
 
 Planes climb to a cruising altitude of six to seven miles above the Earth’s surface because there, the air is far thinner, and against that lessened resistance they can fly faster and use less fuel. 
 
 When they reach that altitude, however, they must maximize the air pressure in the cockpit and cabin — and that puts stress on any component that has weakened over time. 
 
 “Typically, if there was that type of defect, you would expect it to manifest just as it reached the peak” altitude, said Steve Wallace, a former crash investigator for the Federal Aviation Administration. 
 
 In 1988, a hole opened in the fuselage of an Aloha Airlines plane in Hawaii, sucking out a flight attendant. Metal fatigue was blamed in 2002 when China Airlines Flight 611 disintegrated after takeoff from a Taiwan airport, killing all 225 people on board. 
 
 “That airplane had an improper repair after a tail strike,” Wallace said, “and I think this Russian airplane that was in the accident had had a tail strike.” 
 
 The Aviation Safety Network reported that the Metrojet plane suffered a “tail strike” in 2001, a type of incident in which an airplane’s tail hits the runway. The damage took three months to repair, but the jet was certified as airworthy this year by regulators in Ireland, where it was registered. 
 
 The Metrojet crash comes as Russian airlines are facing an economic crunch that has forced Transaero, the country’s second-largest airline, to file for bankruptcy. Russia’s aviation authorities grounded Transaero flights recently over concerns that the airline could not maintain safety standards. 
 
 But historically, Kazbegi noted, Russia’s regional and charter airlines have suffered the majority of the country’s air disasters. And with the recent devaluation of the ruble and the country’s economic crisis, they are struggling to make ends meet. 
 
 Travel to Egypt has declined by about 20 percent this year, said Maya Lomidze, executive director of Russia’s Association of Tour Operators. For charter airlines such as Metrojet, that has meant canceling or rescheduling flights, among other measures. 
 
 “Everyone has been saving in one way or another,” she said. 
 
 Meanwhile, thousands of Russian tourists in Egypt still have to find their way home. 
 
 “Some people are panicked; of course there is fear; many people are still in shock,” Lomidze said. “People are afraid to fly. But one way or another, they have to get home.” 
 
 Halsey reported from Washington. Erin Cunningham and Heba Habib in Cairo, Daniela Deane in London, and Brian Murphy and Ellen Nakashima in Washington contributed to this report. 
 
 Read more: 
 
 Al-Qaeda in Syria calls for revenge attacks on Russia 
 
 Russia defends Syria airstrikes amid claims of blows to U.S.-backed rebels 
 
 Today’s coverage from Post correspondents around the world ||||| Image copyright EPA Image caption Debris was found across a wide area of the Sinai peninsula, Russia says 
 
 A Russian airliner which crashed in Egypt's Sinai peninsula, killing all 224 people on board, broke up in mid-air, a Russian official says. 
 
 Victor Sorochenko, the head of Russia's Interstate Aviation Committee, said it was too early to conclude what caused the crash on Saturday. 
 
 He told reporters debris was found across a 20sq km-wide area of Sinai. So far 163 bodies have been found. 
 
 Russia observed a day of mourning on Sunday after its worst air disaster. 
 
 Mr Sorochenko spoke after visiting the site of the debris, near the village of Hasana. The head of Russia's Air Transport Agency, Aleksandr Neradko, said that "all signs attest to the fact that the aircraft disintegrated in the air at a high altitude". 
 
 Jihadists allied to so-called Islamic State in Sinai, where such groups are active, had made a claim on social media that they had brought down flight KGL9268. 
 
 But Egyptian Prime Minister Sharif Ismail said experts had confirmed that a plane could not be downed at 9,450m (31,000ft), the altitude the Airbus 321 was flying at, by weapons the militants are known to possess. 
 
 President Abdul Fattah al-Sisi also urged caution on Sunday, saying the investigation into the cause was a "complicated matter" that could take months. 
 
 Russian Transport Minister Maksim Sokolov said no evidence had been seen that indicated the plane was targeted, and IS has not produced pictures or video footage to substantiate its claim. 
 
 Analysis by BBC Monitoring found that a video purporting to show the downing of a plane did not appear to be an official IS clip, and was not shared on official IS channels. 
 
 Media playback is unsupported on your device Media caption Sarah Rainsford reports: ''Russia is in mourning for 224 people, killed as they flew back from a holiday in the sun'' 
 
 A number of major airlines - Emirates, Air France-KLM, Lufthansa, and Qatar Airways - have decided not to fly over the Sinai Peninsula until more information is available. Two smaller carriers, flydubai and Air Arabia, also said they would re-route flights, while Etihad Airways said it would avoid only "certain areas of airspace" over Sinai. 
 
 Germany's transport ministry has told German airlines not to follow the same route taken by the Russian plane. 
 
 British Airways said it regularly assessed the safety of its routes. BA said it would not confirm flight routes, but that it "would never fly a route unless it was safe to do so". 
 
 The plane came down early on Saturday, shortly after leaving the resort of Sharm el-Sheikh for the Russian city of St Petersburg. 
 
 Russian and French investigators have joined the Egyptian-led probe, along with experts from Airbus, which is headquartered in France. 
 
 Egyptian officials said some bodies had been recovered within a radius of 5km on Saturday, but that of a three-year-old girl was found 8km from the scene. 
 
 One unnamed official told Reuters the plane appeared to have split in two, with one part burning up and the other crashing into a rock. 
 
 Image copyright EPA Image caption The plane's flight recorders have been recovered and sent for tests 
 
 Image copyright Reuters Image caption One official said the plane appeared to have broken in two 
 
 The plane's flight recorders have been found and sent for analysis, officials said. 
 
 Russia's transport regulator said on Sunday it would check all the airline's A-321 planes, but Kogalymavia said this would not affect their operations. 
 
 Egypt's civil aviation minister Hossam Kamal said there had been no sign of any problems on board the flight, contradicting earlier reports that the pilot had asked to make an emergency landing. 
 
 An Egyptian ground service official who carried out a pre-flight inspection of the plane said the aircraft appeared to be in good shape 
 
 "We are all shocked. It was a good plane. Everything checked out in 35 minutes," the official told AP. 
 
 However, the widow of the plane's co-pilot told Russian TV her husband had complained about the aircraft's technical condition. 
 
 Image copyright EPA 
 
 The plane was carrying 217 passengers, including 25 children, Russian transport authorities said. There were seven crew members on board. 
 
 Most of the passengers were Russian, but at least three were Ukrainian and one Belarusian. 
 
 A plane returning 162 bodies to Russia left Cairo late on Sunday, an airport official said. 
 
 Timeline: the course of flight KGL9268 
 
 05:58 Egyptian time (03:58 GMT): Flight leaves Sharm el-Sheikh, the Egyptian cabinet says in a statement 
 
 06:14 Egyptian time (04:14 GMT): Plane fails to make scheduled contact with air traffic control based in Larnaca, Cyprus, according to Sergei Izdolsky, an official with Russia's air transport agency 
 
 06:17 Egyptian time, approx (04:17 GMT): Plane comes down over the Sinai peninsula, according to Airbus 
 
 11:12 Egyptian time (09:12 GMT): Flight had been due to land in St Petersburg's Pulkovo airport ||||| Media playback is unsupported on your device Media caption President Sisi said the area of Sinai concerned was "under our full control" 
 
 Egyptian President Abdul Fattah al-Sisi has described claims that militants linked to Islamic State brought down a Russian airliner as "propaganda". 
 
 He told the BBC that it was too early to say what had caused the crash. 
 
 The Airbus 321 is thought to have broken up in mid-air over the Sinai peninsula on Saturday, killing all 224 people on board. 
 
 On Monday, the airline Kogalymavia blamed "external influence" for the crash. 
 
 But the head of Russia's Federal Aviation Agency, Aleksandr Neradko, told Russian TV that such talk was premature and "not based on any proper facts". 
 
 President Sisi also warned against jumping to conclusions. "All those interested in the matter are welcome to participate in the investigation," he told the BBC ahead of a visit to the UK. 
 
 "When there is propaganda that it crashed because of Isis (IS), this is one way to damage the stability and security of Egypt and the image of Egypt. Believe me, the situation in Sinai - especially in this limited area - is under our full control." 
 
 Media playback is unsupported on your device Media caption Richard Westcott reports on the ongoing investigation into the crash 
 
 The US director of national intelligence, James Clapper, said there was no "direct evidence of any terrorist involvement yet" adding: "It's unlikely, but I wouldn't rule it out." 
 
 Militants launched an insurgency in the Sinai following the fall of President Hosni Mubarak in 2011. They stepped their attacks after the military overthrew Islamist President Mohammed Morsi in mid-2013. 
 
 A year ago the insurgents renamed their movement Sinai Province and pledged alliance to Islamic State. Hundreds of police and soldiers have been killed. 
 
 After the crash Sinai Province issued a written statement and an audio message saying that it brought down the passenger jet. 
 
 However, experts doubt it possesses the weapons capable of bringing down an airliner. 
 
 Image copyright AP Image caption Debris is spread over a wide area 
 
 The Airbus 321 had been carrying 217 passengers, including 25 children, and seven crew members. Most of those on board were Russians. 
 
 It crashed 23 minutes after taking off from the Egyptian Red Sea resort of Sharm el-Sheikh en route to the Russian city of St Petersburg. 
 
 The plane's flight recorders have been found and sent for analysis. 
 
 Debris was spread across a wide area of Sinai, officials said. 
 
 On Monday, the deputy director of Kogalymavia - which has just renamed itself Metrojet - ruled out a technical fault or pilot error. 
 
 "The only [explanation] for the plane to have been destroyed in mid-air can be specific impact, purely mechanical, physical influence on the aircraft," Alexander Smirnov said. 
 
 "There is no such combination of failures of systems which could have led to the plane disintegrating in the air," he added. 
 
 He said the plane lost speed and started descending rapidly, and the crew made no attempt to get in contact and report about the situation on board. 
 
 The US broadcaster CBS News reported that a US satellite had detected a "heat flash" over the Sinai at the time of the crash. 
 
 It said the data was still being analysed and that although the flash could have been caused by a bomb, a fuel tank or engine explosion was also possible. 
 
 It is believed to be Russia's worst ever air disaster. The bodies of most those killed have been flown back to St Petersburg and identification is under way. 
 
 Timeline: the course of flight KGL9268 
 
 05:58 Egyptian time (03:58 GMT): Flight leaves Sharm el-Sheikh, a statement from the Egyptian cabinet says 
 
 06:14 Egyptian time (04:14 GMT): Plane fails to make scheduled contact with air traffic control based in Larnaca, Cyprus, according to Sergei Izdolsky, an official with Russia's air transport agency 
 
 06:17 Egyptian time, approx (04:17 GMT): Plane comes down over the Sinai peninsula, according to Airbus 
 
 11:12 Egyptian time (09:12 GMT): Flight had been due to land in St Petersburg's Pulkovo airport
– An ominous development in Saturday's crash of a Russian plane in Egypt: The airline says pilot error or technical problems could not have caused the crash of Kogalymavia Flight 9268, leaving unspecified "external activity" in the air as the only possible cause, reports the BBC, which notes that an ISIS affiliate is active in the area where the plane went down and that Moscow hasn't ruled out terrorism as a cause. "The only [explanation] for the plane to have been destroyed in mid-air can be specific impact, purely mechanical, physical influence on the aircraft," says airline deputy director Alexander Smirnov. "There is no such combination of failures of systems which could have led to the plane disintegrating in the air." He says that contrary to some reports, the flight did not send out a distress signal or contact air traffic controllers before it broke up midair, reports the AP. Russian officials, meanwhile, say they've gotten a look at the plane's black boxes and they're in good condition, per the AP. The bodies of around 140 of the 224 victims arrived back in St. Petersburg, the doomed flight's destination, early on Monday, reports the Guardian. A state of official mourning has been declared in the city for what officials say is Russia's deadliest aviation disaster, the Washington Post reports. The Post also reports that major carriers, including KLM and Air France, have decided to avoid flying over the Sinai Peninsula until the cause of the crash is known, though United, the only American carrier to fly over the Sinai, says it does "not see a need" to change its routes immediately.