Travel firm Thomas Cook has cancelled all bookings to Sharm el-Sheikh until at least November.
The Government suspended flights to the Egyptian resort on November 4 last year after an Airbus 321 operated by Russian airline Metrojet crashed, killing 224 people.
Islamic State jihadis claimed responsibility for bombing the jet.
More than 16,000 Britons stranded in the area were brought home on a series of rescue flights amid heightened security.
But no flights have operated between the UK and Sharm since November 17 as the Foreign and Commonwealth Office (FCO) is advising against all but essential travel using the Red Sea resort's airport.
Thomas Cook said it was extending its period for cancelling bookings from May 25 to October 31 because there was "no clear indication as to when the FCO travel advice may change".
The company added that any of its customers who were due to travel to Sharm up to that date can cancel or amend their holiday to another destination free of charge.
British Airways has cancelled its services to Sharm until at least September 15.
Thomson Airways has suspended flights up to May 25, with Monarch taking the same action up to April 18.
EasyJet will not operate flights from Stansted to Sharm up to May 27, while its services from Gatwick, Luton and Manchester are cancelled until at least the end of the summer.
The Association of British Travel Agents has previously said the decision on when to use Sharm airport will be made by the UK Government rather than airlines.
The FCO travel advice states that the UK is working with the Egyptian authorities and liaising with travel companies to enable flights to resume ''as soon as appropriate security arrangements are in place''.