Dozens of passengers due to fly out of Gatwick today were told their flights had been cancelled as French air traffic controllers joined a nationwide strike against pension reforms.

Many travellers were forced to cancel trips or change their travel dates to avoid the disruption. Thirteen flights were axed although staff said passengers were not having to wait around as most had been warned in advance of the cancellations.

A spokeswoman for airport operator BAA said: "Two flights from the South Terminal and 11 from the North Terminal have been cancelled.

"People are not waiting around in the airport. I think most have heard about the cancellations on the news but their travel agents should also have informed them and offered alternatives as the strike has been scheduled for some time."

Flights to other countries were unlikely to be affected.

She added: "There are no other delays I am aware of. It might be some other flights will have to be re-routed to avoid French air space but I am not aware of any great impact at the current time."

British Airways is the airline worst affected with at least six flights to France from Gatwick cancelled. In all only 25 of the normal 120 flights offered by the company were operating from UK airports.

At Gatwick, about five flights to destinations including Paris, Marseille, Toulouse and Nantes were still expected to go ahead.

EasyJet also had to cancel one flight to Nice and Ryanair was also affected.

Most major unions were taking part in the strike to defend the current retirement system, which the French government is trying to reform.

The stoppage officially started at 7pm British Time yesterday.