WASHINGTON (AP) — A Malaysia Airlines plane was sending signals to a satellite for four hours after the aircraft went missing, an indication that it was still flying, said a U.S. official briefed on the search for the plane.

The Boeing 777-200 wasn’t transmitting data to the satellite, but was instead sending out a signal to establish contact, said the official, who spoke on condition of anonymity because he wasn’t authorized to discuss the situation by name.