British Airways has suspended all flights to Cairo for a week as a "security precaution".
The cancellations started on Saturday (20 July). BA is yet to specify what the security concern is.
Passengers due to fly to Cairo on Saturday were handed a letter informing them their flights had been cancelled.
"We constantly review our security arrangements at all our airports around the world, and have suspended flights to Cairo for seven days as a precaution to allow for further assessment," said BA in a statement.
The letter to passengers added: "The safety and security of our customers and crew is always our priority, and we would never operate an aircraft unless it was safe to do so."
German carrier Lufthansa also suspended flights to Cairo on Saturday. Its Cairo schedule resumed on Sunday (21 July).
The Foreign Office has updated its travel advice for Egypt, reflecting the move by BA.
"On 20 July 2019, British Airways announced it was suspending its flights to Cairo for seven days.
"If you are due to travel with British Airways, you should contact the airline on 0844 493 0787 for further information."
The FCO’s advice states: “There’s a heightened risk of terrorism against aviation. Additional security measures are in place for flights departing from Egypt to the UK.”
It also continues to advise against all travel to the North Sinai region of Egypt due to terrorist activity.
This includes all but essential travel to the Red Sea resort of Sharm el Sheikh by air after Russian Metrojet flight 9268 was brought down by a bomb on 31 October 2015 killing all 224 people on board.
Egyptair has continued to fly between the UK and Cairo, as have other airlines to other parts of the country.
Thomas Cook is continuing to fly to Hurghada and Marsa Alam, while easyJet continues to fly to Hurghada from Gatwick.