STORY: Ryanair will have to revise down its passenger traffic estimates for next year.

That was the word from the budget airline's CEO Michael O'Leary to Reuters Wednesday (October 16).

He blamed expected delivery delays of Boeing aircraft.

An ongoing strike at Boeing has raised concerns about worsening delays at the planemaker.

The U.S. firm has already faced challenges with deliveries for much of this year, due to a wider crisis around its safety reputation.

O'Leary said Ryanair was supposed to get 20 deliveries before the end of December.

He said they will probably come now in January and February, but called this 'fine'.

But he warned Ryanair are due 30 aircraft from March to June next year, and wondered when they will arrive.

O'Leary believes Ryanair will have to - quote - 'walk back' traffic growth for next year as he doesn't believe they will receive all 30 orders.

The comments from Europe's biggest budget airline are among the strongest yet on capacity constraints.

Both Boeing and rival Airbus have struggled to meet delivery goals amid supply chain challenges.

O'Leary said he was having weekly talks with Boeing about delivery delays.

He is also due to meet with Boeing CEO Kelly Ortberg in the coming weeks.