No signs of the missing Malaysian jetliner have been found at a spot where Chinese satellite images showed what might be plane debris, Malaysia's civil aviation chief said Thursday, deflating the latest lead in the five-day hunt.
"There is nothing. We went there, there is nothing," Azharuddin Abdul Rahman told reporters in Kuala Lumpur.
Vietnamese officials previously said the area had been "searched thoroughly" in recent days.
The hunt for the Boeing 777 has been punctuated by false leads since it disappeared with 239 people aboard just hours after leaving Kuala Lumpur for Beijing early Saturday.
The plane was heading northeast over the South China Sea when it disappeared, but authorities believe it may have turned back and headed into the upper reaches of the Strait of Malacca or beyond.
Adding to the mystery, The Wall Street Journal reported that US investigators suspect the plane flew on for four hours once it lost contact with air traffic controllers, based on data from the plane's engines that are automatically downloaded and transmitted to the ground as part of routine maintenance programs.
The location where Chinese images showed possible debris is not far from where the last confirmed position of the plane was between Malaysia and Vietnam. The images and coordinates were posted on the website of China's State Administration of Science, Technology and Industry for National Defense.
A Xinhua report said the images from around 11am on Sunday appear to show "three suspected floating objects" of varying sizes in a 20-kilometre radius, the largest about 24-by-22 metres off the southern tip of Vietnam, near an oil rig off where a New Zealand worker claimed to have witnessed a burning object in the sky.
Pham Quy Tieu, deputy transport minister, told The Associated Press that the area had been "searched thoroughly" by forces from other countries over the past few days. Doan Huu Gia, chief of air search and rescue coordination center, said Malaysian and Singaporean aircraft were scheduled to visit the area again Thursday.
Li Jiaxiang, chief of the Civil Aviation Administration of China, said later China had yet to confirm any link between the suspected floating objects and the plane.
Malaysia has come under some criticism for its handling of the search, which currently covers 92,600 square kilometers) and involves 12 nations.
FLYING ON FOR FOUR HOURS?
The Wall Street Journal is reporting that US investigators suspect a missing Malaysian jetliner flew on for four hours once it lost contact with air traffic controllers.
The suspicion is based on data from the plane's engines that are automatically downloaded and transmitted to the ground as part of routine maintenance programs.
The report, based on two anonymous sources, raises questions as to why the Boeing 777 would have been flying without passive or active contact with the ground, and if anyone would have been in control during that time.
US counterterrorism officials are considering whether a pilot or someone else on board intentionally disabled the jetliner's transponders to avoid detection and divert it, the report said.
The plane's last known confirmed position was roughly halfway between Malaysia and Vietnam.
Malaysian authorities have since said they tracked what could have been the plane changing course and heading west.
Investigators have not ruled out any possible cause to explain the disappearance of the plane and the 239 people on board.
"There are issues about the quality of this information," said Steven Wallace, former director of the Office of Accident Investigation at the Federal Aviation Administration, when asked if the turnaround scenario was plausible.
"That question is very much on the table," he said. "What's the quality of this data?"
Uncertainty about the military's claim may explain why the search for the plane continued Wednesday in waters off both sides of the Malaysian peninsula. The chief of Malaysia's air force denied early reports attributed to him that military radar showed the China-bound plane turning back, but said he had "not ruled out the possibility of an air turn-back".
''I am not saying it's Flight MH370. We are still corroborating this,'' said General Rodzali Daud.
The radar used to track the flight after its transponder went dark Saturday morning was no more sophisticated than that used almost 75 years ago by London's defenders during the Battle of Britain.
It sends radio waves into the sky. When those waves encounter something, they bounce back. If the object happens to be the metal skin of an aircraft, it registers as a blob moving across the radar screen.
At the time Flight 370's transponder stopped functioning, the plane was at the outer range of Malaysia's radar. Radar is a line-of-sight instrument that can't look over the horizon, so its reach depends on the altitude of the airplane and on whether the radar equipment is located at ground level or on a mountaintop.
When a transponder is turned on — as is required on all commercial aircraft — it sends a signal to air-traffic controllers that reports the plane's speed, direction, altitude and call sign — in this case, MH370.
Because jetliners file flight plans in advance, a controller can check paperwork to confirm the type of plane — in this case, a Boeing 777.
If the transponder is turned off or suffers an electrical problem, the plane becomes no more than a moving blob on the screen, like a German Stuka dive bomber approaching London.
Air-traffic controllers have access to traditional radar, but they focus on transponder signals, which are referred to as secondary systems.
"The important distinction is that what 99.9 percent of air traffic controllers see is the secondary radar, which means that the controller is seeing information sent by the transponder of the airplane," Wallace said.
"Primary radar is what you need to have if you're trying to see someone who doesn't want you to see them, like an enemy attacking you," he said. "So primary radar is just looking at the reflection of the radar beam off the skin of the airplane, and it's of lesser quality; it doesn't provide any data."
The Malaysian military said that after Flight 370's transponder stopped transmitting, an unidentified airplane was detected at an altitude used only by airliners and military jets.
"That would not happen at high altitude unless it was military," Wallace said. "There wouldn't be any legal civilian operation without a transponder."
Wallace, who has spent decades investigating air crashes, ticked off notable cases in which an airplane has gone off course.
"Korean Airlines 007 in 1983, due to crew error, went off course into Soviet airspace and was shot down," he said. "Crew error is highly unlikely here. This was a way more modern airplane that has a GPS flight management system."
In two cases — involving EgyptAir in 1999 and SilkAir in 1997 — a suicidal pilot was thought to have brought the planes down, he said.
"I'm not suggesting that that was the case here," he said. "What happened here, if you believe this information [from the Malaysian military], was that the changing of course appeared to happen pretty much concurrently with the loss of the transponder. That has to suggest that control of the airplane was taken over by someone unauthorised."
MAP SHOWING WHERE KIWI SIGHTED 'BURNING OBJECT'
THE EMAIL ABOUT A 'BURNING OBJECT'
- Washington Post, with Stuff, AP, Reuters