British Airways and Lufthansa abruptly suspended flights to Cairo on Saturday (July 20) over security concerns.
But the airline carriers gave no details about what might have prompted the move.
In a statement, BA said: "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." Lufthansa later said it had followed suit, halting routes to Egypt's capital city from Munich and Frankfurt.
Though they will resume on Sunday (July 21).
Egyptian airport security sources told Reuters that British staff had been checking security at Cairo airport on Wednesday and Thursday, giving no further details.
The British Foreign Office updated its travel advisory on Saturday to add a reference to the airline's suspension, advising travelers affected to contact the airline.
Egypt's Ministry of Civil Aviation said the British Embassy in Cairo confirmed the decision was not issued by Britain's transport or foreign ministries.
The British government has long advised against all but essential travel by air to and from the Egyptian resort of Sharm el-Sheikh.
A Russian passenger jet was bombed there in 2015, killing all 224 people on board shortly after takeoff.
That attack was claimed by Islamic State.
But it has not previously issued similar warnings against flying to and from Cairo.