AP Airlines Writer
NEW YORK (AP) -- The most dangerous parts of a flight are takeoff and landing. Rarely do incidents happen when a plane is cruising seven miles above the earth.
So the disappearance of a Malaysia Airlines jet well into its flight Saturday morning over the South China Sea has led aviation experts to assume that whatever happened was quick and left the pilots no time to place a distress call.
It could take investigators months, if not years, to determine what happened to the Boeing 777 flying from Malaysia's largest city of Kuala Lumpur to Beijing.
"At this early stage, we're focusing on the facts that we don't know," said Todd Curtis, a former safety engineer with Boeing who worked on its 777 wide-body jets and is now director of the Airsafe.com Foundation.
Military radar indicates that the missing Boeing 777 jet may have turned back before vanishing, Malaysia's air force chief said Sunday as authorities were investigating up to four passengers with suspicious identifications. The revelations add to the mystery surrounding the final minutes of the flight. Air force chief Rodzali Daud didn't say which direction the plane veered when it apparently went off course, or how long it flew in that direction, Some of the information it had was also corroborated by civilian radar, he said.
If the information about the U-turn is accurate, that lessens the probability that the plane suffered a catastrophic explosion but raises further questions about why the pilots didn't signal for help. If there was a minor mechanical failure -- or even something more serious like the shutdown of both of the plane's engines -- the pilots likely would have had time to radio for help. The lack of a call "suggests something very sudden and very violent happened," said William Waldock, who teaches accident investigation at Embry-Riddle Aeronautical University in Prescott, Ariz.
It's possible that there was either an abrupt breakup of the plane or something that led it into a quick, steep dive. Some experts even suggested an act of terrorism or a pilot purposely crashing the jet.
"Either you had a catastrophic event that tore the airplane apart, or you had a criminal act," said Scott Hamilton, managing director of aviation consultancy Leeham Co. "It was so quick and they didn't radio."
No matter how unlikely a scenario, it's too early to rule out any possibilities, experts warn. The best clues will come with the recovery of the flight data and voice recorders and an examination of the wreckage. U.S. investigators from the FBI, the National Transportation Safety Board and the Federal Aviation Administration and experts from Boeing were heading to Asia to assist in the investigation.
A massive international sea search has so far turned up no confirmed trace of the jet, though Vietnamese authorities said late Sunday that a low-flying plane had spotted a rectangular object in waters about 90 kilometers (56 miles) south of Tho Chu island, in the same area where oil slicks were spotted Saturday. The state-run Thanh Nien newspaper said, citing the deputy chief of staff of Vietnam's army that searchers had spotted what appeared to be one of the plane's doors.
Airplane crashes typically occur during takeoff and the climb away from an airport, or while coming in for a landing, as in last year's fatal crash of an Asiana Airlines jet in San Francisco. Just 9 percent of fatal accidents happen when a plane is at cruising altitude, according to a statistical summary of commercial jet airplane accidents done by Boeing.
Capt. John M. Cox, who spent 25 years flying for US Airways and is now CEO of Safety Operating Systems, said that whatever happened to the Malaysia Airlines jet, it occurred quickly. The problem had to be big enough, he said, to stop the plane's transponder from broadcasting its location, although the transponder can be purposely shut off from the cockpit.
One of the first indicators of what happened will be the size of the debris field. If it is large and spread out over tens of miles, then the plane likely broke apart at a high elevation. That could signal a bomb or a massive airframe failure. If it is a smaller field, the plane probably fell from 35,000 feet intact, breaking up upon contact with the water.
"We know the airplane is down. Beyond that, we don't know a whole lot," Cox said.
The Boeing 777 has one of the best safety records in aviation history. It first carried passengers in June 1995 and went 18 years without a fatal accident. That streak came to an end with the July 2013 Asiana crash. Three of the 307 people aboard that flight died. Saturday's Malaysia Airlines flight carrying 239 passengers and crew would only be the second fatal incident for the aircraft type.