British Airways pilots are planning their first-ever strike in London, walking out for 48 hours in a pay dispute.

Most of British Airway’s 850 scheduled flights per day will be cancelled, with passengers being offered a refund or a later flight.

The Guardian newspaper estimates some 145,000 passengers will be affected.

According to the Sydney Morning Herald, the industrial action has affected its Australian operations, with the airline cancelling Tuesday’s scheduled flight from Sydney to London.

The union’s general secretary Brian Strutton said pilots had to accept significant pay cuts during difficult times and now that the airline was making money, it should give something back.

The union estimates the costs to the airline at about STG40 million ($A72 million).

In July, pilots declined an offer of a 11.5 per cent pay rise over three years.