WASHINGTON — A review of emails and a search of a home flight simulator have found nothing to suggest the pilots on missing Malaysia Airlines Flight 370 purposely diverted it from its Beijing destination, according to two U.S. law enforcement officials.
"Nothing stuck out," said one of the sources, who was briefed on the search conducted by Malaysian officials.
The findings Tuesday appeared to undercut theories of a suicide, even as U.S. law enforcement officials continued to focus on hijack scenarios or other means of sabotage, including whether someone preprogrammed some of the aircraft's computer systems to execute the diversion.
"It's still possible that someone entered the cockpit and took the flight a different direction," said one U.S. source, speaking confidentially because the inquiry is ongoing. "Or it was tinkered with beforehand."
An additional theory remains that one of the pilots "took it upon himself" to divert the plane for unknown reasons, the source said.
The crew could have been trying to divert the aircraft toward the Malaysian island of Langkawi, which has a 13,000-foot runway and an easy approach, one commercial pilot suggested in an Internet posting that stirred much discussion Tuesday.
A team of investigators with the U.S. National Transportation Safety Board has been dispatched to Kuala Lumpur, Malaysia's capital. That team is headed by John Lovell, a longtime NTSB investigator with experience in assisting foreign governments with crash investigations.
China's role in the search, now encompassing about 3 million square miles, also appeared to grow Tuesday. The official New China News Agency said two naval groups turned westward, toward the Andaman Islands, and waters southwest of Sumatra, an island in western Indonesia. They join two U.S. anti-submarine surveillance aircraft combing the south Indian Ocean.
Malaysian authorities have been focusing on the crew since declaring Saturday that the Boeing 777's sharp and sudden diversion about 50 minutes into the March 8 flight from Kuala Lumpur resulted from a "deliberate action by someone on the plane."
The U.S. source said his Malaysian counterparts were eager to determine whether the pilot, Zaharie Ahmad Shah, might have been training for such a maneuver on his home simulator, specifically how to turn off the transponders and other in-flight devices. But, the source said, investigators "didn't find that."
He said authorities had discovered nothing particularly disturbing in the pilots' personal lives. The copilot, Fariq Abdul Hamid, was preparing for his wedding, the source said.
Conversations between the cockpit and the air traffic control tower in Malaysia were friendly, routine and professional, with no hint of impending trouble, he said.
U.S. officials believe the plane eventually crashed into water, the source said. "As we get further into this, the percentages rest in the ocean. You have to believe the plane crashed into the ocean."
Pilots have been implicated in several high-profile airplane crashes in recent years, most famously EgyptAir Flight 990 in 1999 and SilkAir Flight 185 in 1997, but in both cases, government officials disputed U.S. investigative findings of pilot suicide.
James E. Rosenberg, a Woodland Hill-based forensic psychiatrist who investigated the SilkAir flight from Jakarta to Singapore, concluded that the Indonesian and Singaporean governments missed warning signs about the pilot's financial problems, impulsive behavior and anger over disciplinary actions.
"You got to understand that typical suicide does not apply here. Pilots are high-functioning, stress-resilient people You are not going to expect that these guys are crying, not shaving, not getting out of bed. You have to look at more subtle signs,'' said Rosenberg. "What turned out to be important was not that he continued to look social and friendly and relaxed in casual contact ... but that privately he was angry and vindictive.''
Rosenberg said the pilot had also taken pains to disguise his culpability in the crash. "In killing himself, he was potentially going to provide extensive insurance for his family. If he was able to make it look like an accident, he would avoid the humiliation to his family."
After Sept. 11, airlines reinforced cockpit doors to deter hijackers, but little has been done to protect aircraft if the pilot is the malefactor. A pilot can turn off the plane's communications or turn off the cabin pressurization, something that could be done to incapacitate passengers.
"What pilots can do is almost limitless. The question is why they would want to do it. What is the motivation?" said Jason Middleton, head of the aviation department at New South Wales University in Sydney, Australia. "If you are going to commit suicide, you'd have to be a hardhearted person to take 238 others with you.''
The Malaysian newspaper Berita Harian reported Tuesday that investigators found software in the simulator for Male International Airport in Maldives, three airports in India and Sri Lanka, and one belonging to the U.S. military base on Diego Garcia.