"We're contracted to get 51 aircraft from Boeing before the end of April. We will be lucky to get 40 aircraft by the end of June next year and that's critical to our continued growth," O'Leary told a Eurocontrol event.

Ryanair plans to grow from a record 168 million passengers this financial year to 185 million next. O'Leary said earlier this month that he was concerned Boeing might fall 5-10 aircraft short, knocking 1 or 2 million from that target.

(Reporting by Padraic Halpin; Editing by Alison Williams)