LONDON — Ryanair, Europe’s biggest airline by passengers, has issued a profit warning for the year amid strikes and rising fuel prices.

The low-cost carrier said it has lowered its guidance by 12%, to between 1.1 billion euros (US$1.28 billion) and 1.2 billion euros for the full year.

Pilot and cabin crew strikes in September hit passenger numbers and resulted in passenger compensation costs.

Ryanair Chief Executive Michael O’Leary says that while the strikes have been successfully managed, “customer confidence, forward bookings and Q3 fares has been affected, most notably over the October school mid-terms and Christmas.” Second and third-quarter traffic and airfares will be “somewhat lower than expected” as a result.

The airline says more staff strikes could force the company to issue further profit warnings.