As many as 9,400 of Ryanair’s 78,000 flights were hit by air traffic control delays in June.
The level of ATC-related disruption doubled over the previous month, the no-frills carrier disclosed.
Air traffic control staff shortages were blamed by the airline.
However, the level of cancelled flights fell dramatically year-on-year from 1,170 in June 2018 to just ten last month.
Chief marketing officer Ryanair’s Kenny Jacobs said: “Regrettably ATC delays have almost doubled in June over May with over 9,000 Ryanair flights suffering ATC delays – with Germany, France, Spain and Austria the worst performing ATC providers.”
Ryanair carried more than 14.2 million passengers last month with over 91% of flights arriving on time, excluding ATC delays.