Pan-pan

The radiotelephony message PAN-PAN is the international standard urgency signal that someone aboard a boat, ship, aircraft, or other vehicle uses to declare that they have a situation that is urgent, but for the time being, does not pose an immediate danger to anyone's life or to the vessel itself. This is referred to as a state of "urgency". This is distinct from a mayday call (distress signal), which means that there is imminent danger to life or to the continued viability of the vessel itself. Radioing "pan-pan" informs potential rescuers (including emergency services and other craft in the area) that an urgent problem exists, whereas "mayday" calls on them to drop all other activities and immediately begin a rescue.
The exact representation of PAN in Morse code is the urgency signal XXX, which was first defined by the International Radiotelegraph Convention of 1927.
Etymology.
As with "mayday" (from "venez m'aider", "come help me"), the urgency signal pan-pan derives from French. In French, a "panne" is a breakdown, such as a mechanical failure. In English, it is sometimes pronounced as and sometimes as .
A three-letter backronym, "possible assistance needed" or "pay attention now" derives from "pan". Maritime and aeronautical radio communications courses use those as mnemonics to convey the important difference between mayday and pan-pan.
Usage.
To declare pan-pan correctly, the caller repeats it three times: "Pan-pan, pan-pan, pan-pan," then states the intended recipient, either "all stations, all stations, all stations," or a specific station, e.g. "Victoria Coast Guard Radio, Victoria Coast Guard Radio, Victoria Coast Guard Radio." Then the caller states their craft's identification, position, nature of the problem, and the type of assistance or advice they require, if any. An equivalent Morse code signal was "X X X", with each letter sent distinctly. 
Nautical examples.
Examples of the correct use of a "pan-pan" call from a boat or ship may include the following cases, provided the skipper or master remains confident they can handle the situation, and that there is no current danger to the life of any person or to the safety of the vessel. Once the urgent situation that led to the pan-pan broadcast is resolved or contended with, conventional practice is for the station that initiated the pan-pan call to make a followup broadcast to all stations, declaring that the urgent situation no longer exists.
A call that originates as a "pan-pan" signal might be followed by a Mayday distress signal if the situation deteriorates to the point of "grave and imminent danger," thus warranting immediate action (intervention, assistance, response) on the part of listeners in accordance with standard operating practices for distress signaling.
Marine rescue organisations, such as Coastal Patrol, Coast Guard, and Search and Rescue listen on marine radio frequencies for all distress calls including "pan-pan". These organisations can coordinate or assist and can relay such calls to other stations that may be better able to do so.
Aeronautical examples.
In September 1998, Swissair Flight 111 used the call during an emergency landing request following a fume event, which turned out to be an electrical fire that subsequently destroyed the aircraft. Also, in the wake of Avianca Flight 52, the call is frequently used to denote situations where fuel is getting low for given conditions, but not yet at a critical emergency state. Qantas Flight QF-74 used the call "pan pan pan" when it had an engine failure on its fourth engine soon after take off from San Francisco. Qantas Flight 72 (QF-72) issued a pan-pan when the aircraft experienced rapid, uncommanded movements in which the plane dropped several hundred feet without instruction from the flight crew. Several passengers and crew suffered major and minor injuries, and so the call was upgraded to "mayday".
On 4 November 2010, Qantas Flight 32 issued a pan-pan when one of its four engines suffered an uncontained engine failure shortly after take-off in a flight from Singapore to Sydney.
On 15 December 2010, an RAF CH-47 Chinook helicopter with serial number ZH891 was on a daytime tasking in flight within the Green Zone in Kabul, Afghanistan when it came under small arms and rocket-propelled grenade fire. A 7.62-mm round penetrated the cockpit and hit the instrument panel, severing 36 wires leading to it from various instruments. The wiring loom was sheared as a result, which caused an instruments failure without damaging vital components. As the Chinook was still able to fly level, pilot Flight Lieutenant Alex "Frenchie" Duncan decided to issue a pan-pan rather than a mayday to Bastion Tower. The Chinook made it back to Camp Bastion safely without further incident.
On 13 April 2010, Cathay Pacific Airways flight CPA780 from Surabaya, Indonesia to Hong Kong issued a pan-pan when one of their engines failed. This was upgraded to a mayday when the second engine also quit shortly thereafter.
On 5 May 2012, Air Berlin Flight 9721, on an Airbus A330 with registration D-ALPA, issued a pan-pan. 15 minutes before touchdown at Munich from Palma, Mallorca, when the crew reported fatigue to the traffic controllers and requested autoland. They in turn had to organize airspace for automatic landing 15 minutes later.
On 12 October 2013, Cyprus Airways flight number CY303 from Vienna to Larnaca, Cyprus, operated by an Airbus 319-100, registration number 5B-DCN, issued a pan-pan over Thessaloniki, Greece, due to a crack on the pilots' windscreen. The pilots immediately descended to 23,000 feet to reduce pressure and the risk of the windscreen breaking. The pilots decided the best solution was to land at Eleftherios Venizelos airport in Athens, Greece, something they managed after 30 minutes of flight.
On 25 August 2014, an 82-year-old passenger aboard a chartered Australia by Air Beechcraft Duchess from Bankstown to Cowra, New South Wales, wrested controls from the pilot in an apparent attempt to cause a crash. After overpowering his passenger and regaining control, the pilot issued a pan-pan and performed a safe emergency landing.
In February 2016, Virgin Atlantic flight VS025 from London to New York City issued a pan-pan when west of Ireland, after the co-pilot reported feeling unwell due to an incident with a laser soon after take-off. The plane returned to Heathrow Airport as a "precautionary measure".
In March 2017, the crew of a Regional Express (Rex) flight ZL768, from Albury to Sydney, issued a pan-pan when one of the two propellers of the Saab 340 plane fell off over the Sydney suburb of Revesby. The aircraft was about 20 km from its destination, and it landed safely at Sydney Airport. The passengers were shaken but uninjured. The propeller was found in bushland at Revesby four days later.
On 5 May 2019, Aeroflot Flight 1492 from Moscow Sheremetyevo to Murmansk (Russia) with 73 passengers and five crew, was in the initial climb when, following a lightning strike, the crew declared pan-pan reporting they had loss of radio communication first, later emergency via transponder codes and returned to Sheremetyevo for a landing on runway 24L at 18:31L (15:31Z). During the roll out the aircraft burst into flames, veered left off the runway and came to a stop on the grass adjacent to the runway, the aircraft burned down. Forty-one occupants perished in the accident (28 occupants still missing were declared dead), 35 occupants were able to evacuate the aircraft via both front door emergency slides, the two flight crew escaped via the escape ropes through the cockpit windows, there were 11 injuries. The aircraft's tail section completely burned down and was destroyed.
On 10 July 2019, Virgin Australia Flight VA69 from Melbourne to Hong Kong, issued a pan-pan when the pilot realised the right engine was leaking fuel shortly after take off from Melbourne. The pilot advised fire crews to be ready and asked for an emergency landing back at Melbourne. Within 60 minutes of take off the aircraft had landed safely back at Melbourne Tullamarine airport and all crew and passengers were disembarked safely.
On 10 December 2020, UPS Airlines Flight 249 from Dublin to Cologne issued a pan-pan when the Boeing 767's right engine failed shortly after takeoff. The crew was able to immediately and safely return to Dublin.
Medical advice.
One special case of "pan-pan" is to ask for medical advice. This is a normal "pan-pan" call that includes a phrase such as "request medical advice" and the craft identification, position, and nature of the medical problem. This type of call is specifically for getting a physician's advice for a medical problem that does not, in the opinion of the skipper or master of the vessel, seem life-threatening. The phrase "pan-pan medico" appears in some older reference books, but is no longer in official use.
Once patched through, a physician or other medical expert on land or in another vessel typically asks the radio operator to detail the symptoms and history of the condition, and provide any available patient medical history. The physician typically recommends first aid treatment and gives other advice based on what resources are available on board. In some cases, the medical issue may be urgent enough to escalate the pan-pan to a mayday call for immediate intervention by rescuers, if possible.