Ryanair's first quarter post-tax profit fell 46%.

On Monday, Ryanair announced that its net profit for the first quarter ended June fell 46% year-on-year, below analysts' expectations, and warned that fares for the key summer months would be "significantly below" the current level.

Ryanair's net profit for the three months ended June was €360m (approximately $392m), far below the average analyst estimate of €538m.

In a statement, CEO Michael O'Leary said that the average fare per passenger fell 15% year-on-year in the first quarter, as the airline was forced to take "more price stimulus than we had anticipated".

"While demand in Q2 is strong, prices remain lower than we had anticipated and we now expect Q2 fares to be significantly below last summer (our previous expectation was flat to slightly up)," Mr O'Leary said, referring to the July-September period, when Ryanair usually makes most of its profits.

Mr O'Leary said it was too early to predict the airline's full-year profit for the year ending March 31.