A total of 102,000 Britons have registered their presence in the Middle East with the UK government, as Iranian strikes continue across the region.
Foreign Secretary Yvette Cooper told the BBC there were an estimated 300,000 British citizens in Gulf countries, where much of the airspace is closed.
She said many of those trapped were holidaymakers, passengers transiting through or people on business visits.
Foreign Office sources said no evacuation was imminent but the government was preparing for potential scenarios if commercial flights remained grounded.
British nationals in Bahrain, Israel, Kuwait, Palestine, Qatar and United Arab Emirates have been urged to register their presence to receive updates from the Foreign Office.
