A signaling system was disabled on the missing Malaysia Airlines jet before a pilot spoke to air traffic control without mentioning trouble, a senior Malaysian official said on Sunday, reinforcing theories that one of the pilots may have been involved in diverting the plane and adding urgency to the investigation of their pasts and possible motivations.
With the increasing likelihood that Flight 370 was purposefully diverted and flown possibly thousands of miles from its planned route, Malaysian officials faced more questions about how the investigation, marked by days of contradictory government statements, might have ballooned into a global goose chase for information.

Prime Minister Najib Razak acknowledged on Saturday that military radar and satellite data raised the possibility that the plane could have ended up somewhere in Indonesia, the southern Indian Ocean, or along a vast arc of territory from northern Laos across western China to central Asia. Malaysian officials said they were scrambling to coordinate a 25-nation effort to find the plane.

… Rohan Gunaratna, a professor at Nanyang Technological University in Singapore who studies security and terrorism in Asia, said that while the weight of suspicion would inevitably fall on the pilots and other crew members, investigators were following established procedure by examining everyone on the missing plane.

“You can’t rule anything out, so everyone on the plane must be treated as a potential suspect,” Professor Gunaratna said in a telephone interview. He said he had heard no credible information of any militant group’s claiming responsibility for seizing the plane.

“That does not mean the possibility does not exist, but at this stage of the investigation it’s important to be open to all the possibilities,” he said.