LONDON (Reuters) - The travel of 3,000 passengers on Saturday was affected by problems at check-in passengers on British Airways flights at three airports in London.

The airline warned of cancellations and delays, as problems came at the height of the summer travel season in the British capital.

A spokeswoman for British Airways said the scale of the problem was not yet fully clear.

The three affected airports are Heathrow, Gatwick and London City.

The airline said it was using manual backup systems to check in and urged passengers to arrive early before their flights.

She stressed that the technical flaw is not a computer problem globally.