Maclean says: “Once you go outside primary radar coverage, which would normally be about 100 miles offshore maximum, you are relying on the plane to be transponding.” [...] 
 
 [Answer continues here] 
 
 Why are the searches taking place over such vastly different areas? Here the aircraft transmits its own signal and gives its position via satellites. At cruising altitude the plane would have been travelling at between 500-600mph – allowing for some considerable distance to be travelled if the plane was still intact when it disappeared from the radar. One possible explanation for the use of the stolen passports is illegal immigration. Analysts warned that it's far too soon to know why the plane went missing or what caused it.
– It's well past midnight in Malaysia, where the search for Flight MH370 is on hold until daylight, but developments are continuing to trickle out—though the updates are far from clarifying ones. The Financial Times follows up a report on the two men—one using an Italian passport, one Austrian—who boarded the plane using stolen passports. A Thai travel agent told the paper that the tickets were booked through an Iranian middleman who goes by "Mr. Ali." She says she has booked tickets for him for the past three years, and there is no indication that "Ali" was aware the passports were stolen; the agent says Ali often booked travel for his contacts. He had asked her to arrange for the tickets March 1, and the men were originally on different airlines: Qatar and Ethiad (they had different end destinations). But the reserved tickets ultimately expired, with Ali reaching out again on Thursday; the men were then booked on Malaysia Airlines. Now Malaysian authorities have given the US images of the two men, a US official tells CNN. Meanwhile: The Wall Street Journal reports that Malaysian authorities are looking into five people who checked into the flight but didn't board—a not uncommon occurrence. Their luggage was removed from the flight before it departed. The search area is now bigger, and includes a portion of the strait of Malacca and more of the South China Sea, per the Guardian. The director general of Malaysia's Department of Civil Aviation says that's an area with a 100-nautical-mile radius, double the previous size. China is lending space satellites to the search.