The European Commission has written to Ryanair seeking information on whether it is breaking European law by cancelling bookings made on third-party websites.
Brussels wants to analyse 'the compatibility' of the airline's new policy with EU law on passengers' rights, according to commission spokesman Antonio Tajani.
The low-cost carrier announced earlier this month that it would not honour what it termed 'unlawful' bookings that were not made on its own website or telephone reservations line.
It said it would start cancelling such reservations from next Tuesday.
Ryanair accused what it called 'screen-scraping' websites such as lastminute and eDreams of levying 'unnecessary' handling charges, of failing to provide up-to-date flight information and of delaying access to the airline's own website by its customers.
Spain's transport ministry is already investigating Ryanair over the decision which Spanish media said could affect about 1,000 air reservations a day in Spain.
The Spanish-based eDreams website vowed Thursday to take 'suitable legal measures' if Ryanair violates the rights of its customers.
The airline has already taken legal action against two sites, Ireland's Bravofly and V-tours of Germany, to prevent them from listing Ryanair flights
