Doomed Flight MS804 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.
Mr Azmy said that in the minutes before the EgyptAir plane disappeared it was flying at its normal altitude of 37,000 feet, according to the radar reading.
His comments came as hundreds of mourners attended a memorial service for the 66 victims at the Al Mosheer Tantawy mosque in Cairo.
Mr Azmy said: 'That fact degrades what the Greeks are saying about the aircraft suddenly losing altitude before it vanished from radar.
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.
Meanwhile a French ship yesterday 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.
Some aviation experts have also said the erratic flight reported by the Greek defence minister suggests a bomb blast or a struggle in the cockpit.
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 uncommon yet is highly unlikely to cause a crash.
Egypt, which is sending a submarine to search for the flight recorders, 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.
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.
Yesterday, the remains of the first victims began arriving at a morgue in Cairo to start the long and painful process of identifying the bodies which have been described as 'unrecognisable'.
More than 20 body bags containing parts of corpses recovered from the Mediterranean crash site were brought to the Zenhom morgue by the Egyptian Army at midnight on Sunday.
Close family members began arriving at the morgue yesterday morning after being invited to give DNA samples to aid their identification.
A forensic source said: 'There is no complete body. There are only body parts. They are unrecognisable.
It comes as hundreds of mourners attended memorial services over the weekend for some of the 66 victims of the EgyptAir plane which mysteriously crashed into the Mediterranean on Thursday.
The mystery of the crash also deepened over the weekend amid reports the pilot spoke about 'an emergency descent' aimed at putting out a fire on board.
It was initially claimed Mohamed Said Ali Ali Shoukair lost all radio contact before the Airbus A320 plunged into the sea last Thursday, killing all 66 people on board, en route from Paris to Cairo.
But aviation sources in Paris have now said he contacted Egyptian air traffic controllers to say he was going to make an emergency landing because there smoke filling the plane.
There was 'conversation several minutes long' between Captain Shoukair and the controllers, which amounted to 'a distress call', according to French TV station M6.