Not only 2 passengers travelling on stolen passports, the Chinese redacting the name of one passenger from the Xinjiang province, one Russian listed on the passenger manifest denying he was on the flight, now the FBI are getting involved.
FBI to investigate disappearance of a Malaysian Airlines jet - latimes.com
No "evidence" of terrorism according to FBI officials, though "images they find can be used with the bureau's vast counter-terrorism technology to look for matches with known members of Al Qaeda or other terrorist organizations"