Wizz Air Holdings Plc is considering releasing another batch of its annual unlimited flights passes after the first 10,000 sold out in 48 hours.

The Hungary-based carrier is “still assessing the option to launch another set” of its €499 ($556) All You Can Fly passes, a spokesman said. The offer, which was announced on Aug. 13, brought an implied €5 million into the airline’s coffers during what’s been a disappointing summer.

The promotion is a bright spot for Wizz, which cut its annual profit outlook this month over engine issues that grounded some of its Airbus SE A321 aircraft. Other airlines in Europe have also cut their profit forecasts amid notable declines in airfares this summer. 

The 12-month plan comes with caveats, including only allowing customers to book flights three days ahead of their departure and a mandatory €10 booking fee on each flight booked. Luggage and seat selection aren’t included in the membership. 

Michael O’Leary, the chief executive officer of larger rival Ryanair Holdings Plc, described Wizz’s offer as a “marketing scam” in a Newstalk interview, saying that there won’t be any seats available on the aircraft if customers could only book three days before the flight. 

Wizz Chief Corporate and ESG Officer Yvonne Moynihan said in a separate Newstalk program that O’Leary’s comments were “not only provocative but they were also inaccurate.”