British Airways has cancelled two flights because of a security threat.
Flight 223 from Heathrow to Washington's Dulles Airport will not fly this Sunday. Monday's Flight 263 from London to Riyadh, Saudi Arabia is also scrapped.
BA said the decision "follows government advice to cancel those flights for security reasons".
"We apologise to our customers booked to travel on these flights for the inconvenience caused," it said.
Flight 223 has been delayed or cancelled eight times this year because of US security alerts. Saudi flights also have been grounded several times.