Ryanair Chief Executive Michael O'Leary said it was a "scandal" that French strikes had blocked many overflights, disrupting services between different countries such as the busy tourist market between Britain and Spain.

Airlines have to compensate passengers for long delays or cancellations under European passenger-rights laws but are unable to recover penalties from air traffic authorities when airspace is blocked, he told the A4E Aviation Summit in Brussels.

Tension between airlines and French controllers has been a recurring issue but escalated this year amid France's growing political crisis over changes to the retirement age.

France's DGAC aviation authority said it was applying minimum service rules for some flights but the airline industry wants this to apply to overflights, as well as domestic trips.

O'Leary said airports were better prepared for delays this summer after widespread chaos last year but that he expected further air traffic control problems in coming months.

Airline leaders meeting in Brussels also stepped up calls for longer-term reforms to Europe's fragmented airspace, which is separated along national lines, resulting in delays.

The European Commission has been working for years on a long-delayed reform called Single European Sky but political analysts say it is being held up by individual nations worried about the impact on jobs at national control centres.

EU Transport Commissioner Adina-Ioana Valean told the conference she hoped for some progress on the topic later this year.

(Reporting by Tim Hepher, Joanna Plucinska; Editing by Andrew Heavens and Emelia Sithole-Matarise)