Speculation in the British and American media has - without any evidence - blamed mechanical failure, a struggle between the crew, a bomb, a hijack and a suicidal crew member. The lack of any "steer" from America's National Transportation Safety Board investigators has to some extent encouraged the theories. But the nationality of the crew and the plane has also apparently encouraged reporters' irresponsible guesswork.
In previous crashes, infighting between American investigating agencies has contributed to conflicting theories. This time, the authorities have sought to stop speculation by focusing on the facts. But anonymous sources from one US agency have repeatedly leaked their views to the press.
The earliest indications from the cockpit voice recorder are that there was a problem with the aircraft, the crew tried to deal with it, but things went rapidly from bad to worse.
"Something happens. Alarms go off. Both [pilots] work to try to fix it," an unnamed source said after the investigators listened to the tape for the first time. "There is some kind of problem that they're dealing with. It gets progressively worse. And the tape stops."
This source, however, apparently did not speak Arabic and had not understood anything on the tape, which tends to undermine his credibility.
From the aircraft's flight data recorder, it is known that for some reason the crew disengaged the autopilot. The plane began dropping from 33,000ft at a 40-degree angle, almost reaching the speed of sound and zero gravity inside the cabin. The engines were apparently manually shut down during the dive. The plane reached 16,000ft and then climbed back to 24,000ft before falling rapidly and breaking up. This pattern of events does not fit with any known course of action in response to a problem.
There was no indication of a fight between the crew, who were speaking "like pals," said the source who has heard the tape. Nor was there any sign that someone had entered the cockpit. Indeed, there was never any evidence for this theory.
A US government official told Newsweek magazine that Boeing was "pushing" the theory of a cockpit struggle. Boeing denied this. If mechanical failure is the cause, there might be serious implications for Boeing, including legal action.
The supposition of a cockpit fight was based on the fact that the flight elevators had been moved in opposite directions moments before the crash. From this, the inference was drawn that the pilot and co-pilot acted against each other. Equally, it assumed the decision to shut off the autopilot and the engines was irrational, something that cannot be judged until the cause of the problem is known.
The accusation that one of the crew might have tried to kill himself, or have fought with his colleagues, was based on no evidence. It seems highly unlikely that US newspapers would have made these accusations against an America pilot who had died in similar circumstances, and the families and friends of the crew have understandably responded angrily.
Captain Ahmed al-Habashy, the lead pilot, was stable and happy, his wife and brother have said. He was close to retirement. "He never smoked or drank alcohol," his brother said. "He had no bad habits. He was very religious and prayed and was always reading the Koran," he said. The Boston Herald felt it necessary to add that he was "not an extremist".
Co-pilot Adel Anwar was due to be married five days after the flight and had exchanged slots with another flight officer to return home sooner.
Other theories with equally little evidence have also surfaced. The first was that the reverse thrusters might have malfunctioned, based on a similar crash of a Boeing 767 in Thailand - an aircraft that was made at the same time as the EgyptAir plane. The data recorder seemed to rule this out.
More than one newspaper has blamed terrorism, citing the flight profile, the suddenness of the problem and the lack of a distress call. It has also been noted that the aircraft had a large number of Egyptian military personnel on board. The FBI has given no signs that it is actively looking at terrorism as a likely cause. But the leaks from the inquiry may come from the FBI, which has been criticised for a number of investigations recently, and is seeking funds for, among other things, a new counter- terrorism unit.