DUBLIN, May 20 (Reuters) - Ryanair on Monday posted a 34% year-on-year increase in annual profit to a record 1.92 billion euros ($2.09 billion), and expressed "cautious optimism" that peak summer fares would be flat to modestly ahead of last year.

The result was slightly ahead of the 1.91 billion euros profit expected by analysts.

The Irish airline, Europe's largest by passenger numbers, also said it would be 23 jets short of the number Boeing was due to deliver by the end of July and there remained a risk that deliveries could slip further. ($1 = 0.9190 euros) (Reporting by Padraic Halpin; Editing by Jamie Freed)