As many as 63,000 Ryanair passengers were affected as the UK air traffic control meltdown forced the cancellation of more than 350 flights.
The totals emerged as Europe’s largest low fares carrier reported that more than 103,000 flights were operated in August.
Passenger levels rose by 11% year-on-year to 18.9 million with a load factor of 96%.
Ryanair complained that the Nats air traffic control computer failure on August bank holiday Monday has still not been explained.
The airline said flights had to be cancelled on both August 28 and 29.
However, Ryanair saw annual passenger numbers rise by 20% to give a rolling total of 177.4 million.
Meanwhile, rival Wizz Air reported an almost 24% increase in August passenger numbers to 6.1 million with an improved load factor of 94.1%.