The Thai military was receiving normal flight path and communication data from the Boeing 777-200 on its planned March 8 route from Kuala Lumpur to Beijing until 1:22 a.m., when it disappeared from its radar.

Six minutes later, the Thai military detected an unknown signal, a Royal Thai Air Force spokesman told CNN. This unknown aircraft, possibly Flight 370, was heading the opposite direction.

Malaysia says the evidence gathered so far suggests the plane was deliberately flown off course, turning west and traveling back over the Malay Peninsula and out into the Indian Ocean.

But investigators don’t know who was at the controls or why whoever it was took the plane far away from its original destination.

The Thai data is the second radar evidence that the plane did indeed turn around toward the Strait of Malacca.

It follows information from the Malaysian Air Force that its military radar tracked the plane as it passed over the small island of Pulau Perak in the Strait of Malacca.

“The unknown aircraft’s signal was sending out intermittently, on and off, and on and off,” the spokesman said. The Thai military lost the unknown aircraft’s signal because of the limits of its military radar, he said.

The radar data is an encouraging sign that investigators are on the right track, but they still are not sure where the plane ended up.

The latest findings say the plane’s last known location detected by a satellite is somewhere along two wide arcs: one stretching north over Asia and the other south into the Indian Ocean. The plane’s last electronic connection with the satellite was about six hours after it last showed up on Malaysian military radar.

The total area now being searched stands at 2.24 million square nautical miles, Hishammuddin Hussein, the Malaysian defense and transport minister, said at a news conference Tuesday. That’s an area nearly the size of the continental United States.

“This is an enormous search area,” Hishammuddin said. “And it is something that Malaysia cannot possibly search on its own. I am therefore very pleased that so many countries have come forward to offer assistance and support to the search and rescue operation.”