A Number 10 spokesperson said:
We want to update you on our response to the plane crash in Sinai this weekend.
Since then, we have been following the investigation closely to make sure that we take any steps necessary to ensure the safety of British citizens on flights from Sharm. That will always be our priority.
The Prime Minister called President Sisi yesterday evening to discuss what measures the Egyptians are taking to ensure the tightest possible security arrangements at Sharm el-Sheikh airport.
While the investigation is still ongoing we cannot say categorically why the Russian jet crashed. But as more information has come to light we have become concerned that the plane may well have been brought down by an explosive device.
In light of this and as a precautionary measure we have decided that flights due to leave Sharm for the UK this evening will be delayed. That will allow time for a team of UK aviation experts, currently travelling to Sharm, to make an assessment of the security arrangements in place at the airport and to identify whether any further action is required. We expect this assessment to be completed tonight.
In terms of flights from the UK to Sharm, there are no more departures today.
We would underline that this is a precautionary step and we are working closely with the airlines on this approach. The Prime Minister will chair a COBR at 6:45pm to review the situation and we will provide an update after that meeting.
We recognise that this information may cause concern for those in Sharm and indeed for those planning to travel to Sharm in the coming days. We have deployed extra consular staff to Sharm who will be on hand at the airport, working with the airlines, to assist British holidaymakers there. For others, either in resorts at Sharm or planning a holiday to Sharm in the coming days, our advice is to contact your airline or tour operator.