For short flights of up to 1,500km, such as Gatwick-Barcelona, the payment is €250; for flights between 1,500 and 3,500km, such as Heathrow-Athens, it is €400; and for longer flights, above 3,500km, €600.
On Saturday night, travellers spent the night sleeping on yoga mats spread on terminal floors after BA cancelled all flights leaving the London hubs, while disruption continued into Sunday with dozens more services from Heathrow axed.
Earlier the airline's chief executive said the outsourcing of jobs was not to blame for a "catastrophic" IT failure. Customers should get in touch with us directly via our Manage My Booking tool on ba.com or our contact centres so that we can re-book or re-route them to their destination as quickly as possible.
"While the costs of passenger compensation and refunds could well run into the tens of millions, the whole sorry episode has undeniably put a dent in BA's reputation for delivering a premium service".
BA has advised that customers displaced by flight cancellations can claim up to £200 a day for a room (based on two people sharing), £50 for transport between the hotel and airport, and £25 a day per adult for meals and refreshments.
All check-in and operations systems were affected, and the airline cancelled all flights from London's Heathrow and Gatwick airports on May 27.
As stated by British Airways, the IT systems are now "back up and running" and the airline aims to operate the majority of flights departing from Heathrow Airport and attain an nearly normal schedule at Gatwick Airport.
We believe the root cause was a power-supply issue and we have no evidence of any cyber attack.
When asked for details about what exactly happened, a BA spokeswoman did not elaborate on the statement above about an exceptional power surge.
Thousands of passengers queued for hours in departure halls at the airports on a particularly busy weekend. Alternatively, they can rebook for dates through the end of November.
"British Airways' IT failure over the weekend is clearly a PR nightmare and will take a real focus in terms of handling customers' complaints and compensations claims in order to rebuild trust and confidence with the public", said Mark Simpson, analyst at Goodbody.
It is already facing declining customer ratings following unpopular decisions made as it faces competition from low-priced airlines. He also denies this had anything to with cutting IT costs.
"I do not, however, expect the outage to have lasting financial repercussions for the group".
British Airways (BA) said May 30 it had fully recovered its schedules after the major weekend IT crash that grounded the airline's fleet across the world.
While other airlines have been hit by computer problems, the scale and length of BA's troubles were unusual.