It could be "some time" before all UK tourists stranded in Sharm el-Sheikh are home but it is vital to ensure their safety, the prime minister has said, after the suspension of flights.
David Cameron said it was "increasingly likely" a "terrorist bomb" caused a Russian passenger jet to crash on Saturday killing all 224 people on board.
The Foreign Office said its security experts were working to resume flights between the UK and the Egyptian resort.
About 20,000 Britons are said to be in the resort, including 1,000 residents.
Speaking after chairing a meeting of the government's emergency committee Cobra, Mr Cameron said: "The decisions that I'm taking are about putting the safety of British people first.