The Cypriot (search) plane that crashed and killed all 121 people aboard flew on autopilot to its Athens destination — but passed thousands of feet above the airport runway, the chief accident investigator told The Associated Press Thursday.

Helios Airways (search) Flight ZU522 then turned toward the sea, flying in a holding pattern for more than an hour before changing course again and crashing into a mountain north of Athens.

Chief investigator Akrivos Tsolakis told AP that an air traffic control diagram showed the plane had flown on automatic pilot to the Greek capital's international airport. But it was flying at 34,000 feet and turned south into a holding pattern over the island of Kea (search).

"What troubles us is that the automatic pilot was functioning up to a certain point, and then it was disengaged, possibly by human action," Tsolakis said.

He said the automatic pilot had been programmed to fly the plane up to Athens' airport and it was unclear how or why it was disengaged.

"Possibly, there was human intervention. I'm not speaking with certainty, because I don't have all the evidence yet," Tsolakis stressed.

Investigators are examining whether the 115 passengers and six-member crew aboard the Boeing 737-300 had lost consciousness, possibly just after takeoff. The aircraft appears to have flown from Cyprus to Athens on autopilot — a flight of about an hour and a half.

Tsolakis' comments were the first official confirmation that the autopilot was disengaged after the plane flew over the Athens airport. That could give credence to speculation that somebody tried to take control of the plane before it crashed.

The strange circumstances of the flight — and disturbing scenes witnessed by F-16 fighter pilots sent to intercept the plane — have baffled authorities. Officials have said there were no indications of sabotage or terrorism.

According to the government, the two F-16 fighter pilots — who first established visual contact with the plane while it was flying above Kea — reported seeing the co-pilot slumped over the controls, apparently unconscious. They said the pilot was not in his seat, and they later saw what appeared to be two people trying to regain control of the plane. Oxygen masks also were seen dangling from the ceiling of the passenger cabin.

Tsolakis said investigators were still examining the possibility that those on board lost consciousness because of sudden cabin decompression.

A six-member team of coroners also was conducting toxicology tests on some of the bodies to determine whether the passengers and crew might have inhaled something — possibly carbon monoxide — that rendered them unconscious. Results of those tests were expected by the weekend.

A total of 118 bodies have been recovered from the crash site. Crews were still searching for three bodies, but Kalogrias said they might never be found.

"This is, unfortunately, the consequence sometimes of the impact of a plane crash," he said.

Autopsy results on 26 bodies identified so far have shown passengers and at least four crew members — including the co-pilot — were alive, but not necessarily conscious, when the plane went down. The body of the plane's German pilot has not been identified, and it was unclear whether he was one of the three still missing.

Some answers could be provided by the contents of the plane's flight data recorder, or black box, which has been sent to Paris for decoding.

Tsolakis has he has never encountered such a case. "In my career, going back 50 years as an airman and as a safety officer, I have never seen anything that resembles this," he said.