The doomed EgyptAir Flight 804 did not swerve or lose altitude before it disappeared off radar, the head of Egypt's state-run provider of air navigation services has said.
The comments by Ehab Azmy, head of the National Air Navigation Services Company, challenged an earlier account by Greece's defence minister.
Yesterday, a French ship joined the international effort to hunt for the black boxes and other wreckage of the flight, which crashed into the Mediterranean, killing all 66 people on board.
Five days after the air disaster, questions remain over what happened to the jet before it disappeared off radar at around 2.45am local time on Thursday.
Egyptian authorities said they believe terrorism is a more likely explanation than equipment failure, and some aviation experts have said the erratic flight reported by the Greek defence minister suggests a bomb blast or a struggle in the cockpit.
But so far no hard evidence has emerged.
A 2013 report by the Egyptian ministry of civil aviation records that the same Airbus 320 made an emergency landing in Cairo that year, shortly after taking off on its way to Istanbul, when one of the engines "overheated".
Aviation experts have said that overheating is highly unlikely to cause a crash.
Mr Azmy told The Associated Press that in the minutes before the plane disappeared it was flying at its normal altitude of 37,000 feet, according to the radar reading.
"That fact degrades what the Greeks are saying about the aircraft suddenly losing altitude before it vanished from radar," he said.
"There was no turning to the right or left, and it was fine when it entered Egypt's FIR (flight information region), which took nearly a minute or two before it disappeared."
According to Greece's defence minister Panos Kammenos the plane swerved wildly and dropped to 10,000 feet before it fell off radar.
Greek civil aviation authorities said all appeared fine with the flight until air traffic controllers were to hand it over to their Egyptian counterparts.
The pilot did not respond to their calls, and then the plane vanished from radars.
Egypt, which is sending a submarine to search for the flight recorders, has also refuted earlier reports alleging that search crews had found the plane's black boxes - which could offer vital clues to what happened in the final minutes of the flight.
Ships and planes from Britain, Cyprus, France, Greece and the United States are taking part in the search for the debris from the aircraft, including the black boxes.
Some wreckage, including human remains, has already been recovered.
The French vessel that joined the effort is equipped with sonar that can pick up the underwater "pings" emitted by the recorders.
The search area is roughly halfway between Egypt's coastal city of Alexandria and the Greek island of Crete, where the water is 8,000 to 10,000 feet deep.