NEW YORK, Feb 1: More US-bound flights from England, Scotland and France were cancelled on Saturday and Sunday amid fears Al-Qaeda may be planning a chemical or biological attack on an aircraft.

Underscoring the concerns that terrorists may use the Muslim holiday season of Eid to carry out such attacks, US intelligence agencies have geared into action forcing, among others, American carrier Continental Airlines, Air France and British Airways to cancel flights.

However, the threat information that led to the cancelled flights this weekend did not indicate a specific method to bring down a plane or spread an illness such as smallpox, a US official told American reporters.

Instead, the official said intelligence analysts use information about the flights, and married it to information about types of attacks Al Qaeda may want to launch, to come up with possible scenarios for an attack at any particular time.

British Airways grounded the same flight scheduled for Sunday and Monday from London's Heathrow Airport to Dulles International Airport outside Washington, as well as the return flights. Also cancelled was a flight from London to Miami on Sunday. In addition, Continental Airlines said it cancelled Sunday's Flight 17 from Glasgow, Scotland, to Los Angeles with an intermediate stop in Newark, New Jersey.

Air France scrubbed the same flight set for Sunday and Monday from Charles de Gaulle Airport in Paris to Dulles in Washington. As a result, the return flights were cancelled.