China had sparked talk of a breakthrough in the riddle of the Malaysia Airlines (MAS) jet with satellite images of three large floating objects near where flight 370 with 239 people on board lost contact on Saturday, en route from Kuala Lumpur to Beijing.
But Vietnamese and Malaysian planes that searched the area in the South China Sea on Thursday found no sign of wreckage of the Boeing 777, which has one of the best safety records of any jet.
Adding to confusion, the Wall Street Journal reported that U.S. investigators suspected the plane flew for four hours after its last known contact with air traffic control at 1:30 a.m. Malaysian time, based on data automatically sent from its Rolls-Royce engines.
It would mean flight MH370 traveled for hundreds of miles after it dropped off the radar, expanding the potential crash site far beyond the vast zone under scrutiny now.
The WSJ said U.S. counterterrorism officials were probing the possibility that a pilot or someone else on board diverted the jet towards an unknown location after turning off its communication transponder.
But Malaysia denied the report as “inaccurate.”
“The last (data) transmission from the aircraft was at 0107 hours which indicated that everything was normal,” Transport Minister Hishammuddin Hussein told reporters.
“Rolls-Royce and Boeing teams are here in Kuala Lumpur and have worked with MAS and investigation teams since Sunday. These issues have never been raised.”
He added that China had told Malaysia that the satellite photos posted on the website of a Chinese state science agency were released “by mistake and did not show any debris.”
'Every day like eternity'
The day of Malaysian denials only exacerbated the puzzles surrounding the search for flight MH370, which has been blighted by false alarms, swirling rumors and contradictory statements about its fate.
Authorities have chased up all manner of leads, including oil slicks, a supposed life raft found at sea and even witness accounts of a night-time explosion, only to rule them all out.
“Every day it just seems like it's an eternity,” Danica Weeks, whose husband Paul was on board, told CNN from their home in the Australian city of Perth.
Fighting back tears, she described how Paul had left his wedding ring and watch with her for safekeeping before starting his journey to a mining venture in Mongolia.
“I'm praying that I can give (them) back to him. It's all I can hold onto. Because there's no finality to it and we're not getting any information,” she said.
Malaysia has contributed to the confusion by saying the plane may have turned back after taking off.
Military radar detected an unidentified object early Saturday north of the Malacca Strait off west Malaysia but it is unclear if it was the missing airliner.
The search for the plane now encompasses both sides of peninsular Malaysia, over an area of nearly 27,000 nautical miles (more than 90,000 square kilometers) — roughly the size of Portugal — and involves the navies and air forces of multiple nations.
Theories about the possible cause of the disappearance range from a catastrophic technical failure to a mid-air explosion, hijacking, rogue missile strike and even pilot suicide.
Beijing will keep up the search “as long as there is a glimmer of hope,” Chinese Premier Li Keqiang said.
The passengers included 153 Chinese citizens, and Li told his once-a-year news conference: “Those people's families and friends are burning with anxiety.”
The satellite information prompted the focus of the search to swing back Thursday to the original flight path, after a shift in recent days to Malaysia's west coast — far from the last known location.
“We will look at all areas especially the ones with concrete clues,” a spokesman for Malaysia's civil aviation department said.
The China Center for Resources Satellite Data and Application said in a statement on its website earlier this week that it had deployed eight land observation satellites to scour the suspected crash area.
By Tuesday morning, it had obtained images covering 120,000 square kilometers, describing their quality as “rather good.”
China has also requested assistance from a fleet of Earth-monitoring satellites under an international charter designed to aid emergency efforts.
U.S. authorities said their spy satellites had detected no sign of a mid-air explosion.
Malaysian police said Thursday they were investigating the two pilots, after an Australian television report of a past cockpit security breach, although the transport minister denied that their homes had been raided.
Malaysia Airlines has said it was “shocked” over allegations that First Officer Fariq Abdul Hamid, 27, along with a fellow pilot, violated airline rules in 2011 by allowing two young South African women into their cockpit during a flight.
It also emerged that months before the Malaysia Airlines jet vanished, U.S. regulators had warned of a “cracking and corrosion” problem on Boeing 777s beneath their satellite antenna that could lead to a drastic drop in cabin pressure and possible mid-air break-up.
But Gerry Soejatman, a Jakarta-based independent aviation analyst, said the warning did not apply to the missing aircraft, a Boeing 777-200ER, which has a different kind of antenna.
“When an aircraft simply disappears from radar with no trace whatsoever, normally it means a rapid deterioration of the aircraft — an explosion or structural failure that's very rapid,” he added.
“That means the wreckage would be found near where it was last reported. But in this case, this doesn't seem to be the case.”
On Thursday, Malaysia Airlines said it would retire the flight codes MH370 and MH371 — the return flight from Beijing to Kuala Lumpur — as a mark of respect.