Ryanair has revealed it cancelled some 650 flights in July because of air traffic delays, while rival Wizz Air said the global technology outage directly disrupted about 1% of its flights.
The two airlines reported the impact of disruption as they unveiled how many passengers they flew last month.
Low-cost airline Ryanair said it flew 20.2 million passengers in July, an 8% jump on the 18.7 million people on its flights the same time last year.
It reflects growing demand after the company said its airfares were set to be substantially cheaper over the peak summer months.
Ryanair operated more than 110,500 flights in July, but revealed that 651 flights were cancelled because of air traffic control delays.
Chief executive Michael O’Leary recently said the group “suffered a serious deterioration in European air traffic control capacity which caused multiple flight delays”.
The service has been affected by staff shortages and equipment issues which led to delays to flight schedules and cancellations.
Mr O’Leary called for reform of the service which he described as “hopelessly inefficient”.
Meanwhile, rival budget airline Wizz Air said about 1% of its scheduled flights in July were impacted by a flawed update rolled out by cybersecurity firm CrowdStrike, which led to major disruption around the world.
IT system outages led to flight cancellations, affected some healthcare systems, and crashed millions of computers using Windows.
Wizz Air also revealed that it carried 5.9 million passengers last month, 1.4% less than the six million it flew the previous year.
It also blamed jet engine issues grounding some planes for a dip in its seat capacity, as well as for increased emissions as it was forced to use older planes.