Ukraine's President Petro Poroshenko said the plane may have been shot down over the conflict zone by pro-Russia rebels, and called the tragedy an "act of terrorism".
Speaking in Detroit, US Vice President Joe Biden was cited by the BBC as saying the airline was shot down, "not an accident, blown out of the sky".
The militants, however, have denied it, the BBC reported on Thursday night. In recent days, several Ukraine military jets have allegedly been shot down by the rebels.
Passengers on the jet, which was making its way to Kuala Lumpur from Amsterdam, reportedly included seventy-one Dutch people, 23 Americans, nine Britons and four French citizens. No Italians have as yet been reported to have been on board.
Other airlines have rerouted aircraft including British Airways, Lufthansa, Turkish Airlines, Aeroflot, Air France and Virgin.
Malaysian Airlines said it lost contact with the flight as it flew over eastern Ukraine towards the Russian border.