A British Airways flight to Washington has left London more than three hours late, after being canceled Thursday and Friday because of security concerns.

An airline spokeswoman said the delay was caused by detailed security checks. The afternoon British Airways flight from London to Washington was canceled the past two days because of fears of a possible terrorist threat. Reports said a suspect named on a U.S. terrorist watch list had intended to hijack the plane and crash it into a target in Washington.

The flight is one of three that British Airways operates to Washington daily. The other two have not been affected.

British Airways also canceled Saturday's flight from London to Saudi Arabia's capital, Riyadh, citing security concerns. The airline said it has not yet decided whether to operate the Riyadh flight on Monday.

More than a dozen international flights have been delayed or canceled in the last several days and U.S. fighter jets have escorted some others while in U.S. airspace. International airlines have been asked to put sky marshals on some flights to the United States.