British Airways staff are confident they will be able to handle as many as 49,000 passengers on each of the first two planned strike days - tomorrow and Sunday.
This compares with a figure of around 75,000 for a normal weekend day in March, with some passengers due to travel with other carriers on specially-chartered planes.
This weekend, BA will be operating all flights to and from London City airport and all long-haul flights to and from Gatwick airport in West Sussex.
The airline plans to run 50% of its short-haul Gatwick services, about 60% of its Heathrow long-haul services and about 30% of its Heathrow short-haul flights.
A BA spokeswoman said today: "We would normally operate around 400 to 450 flights on a weekend day. We're hoping to be able to get around 65% of our passengers away this weekend."
BA has arranged with more than 60 other airlines to take BA customers on their flights on the first strike days.
While some passengers whose flights have been cancelled will be travelling on other carriers, others have arranged to fly with BA at a later date and some have opted to get a refund.
To add to BA's problems over the weekend, passengers will not be able to travel directly between central London and Heathrow on the Underground.
This is due to planned engineering work which will close the Tube's Piccadilly line between Hammersmith and Northfields and between Hammersmith and Ealing Common in west London.
Buses will replace trains on the affected section of the line. Heathrow Express main line trains will be operating as normal.