What happened

Shares of discount European airliner Ryanair Holdings (NASDAQ:RYAAY) (LSE:RYA) shed 16.5% of their value on Monday, hurt by rising fuel costs and a damaging strike among employees in Belgium, Germany, Holland, Portugal, and Spain -- and the earnings warning that resulted from these events.

So what

Ryanair pilots in Germany, and Ryanair cabin workers elsewhere in Europe, called a one-day strike on Friday that disrupted the travel plans of more than 40,000 flyers and forced Ryanair to cancel some 250 flights.

A secondary consequence of the strikes was that Ryanair also had to roll back its forecast for this year's "fiscal 2019" earnings. In an update issued today, the airline warned that full-year profit will probably land somewhere between 1.1 billion and 1.2 billion euros, or about 12% below the previous prediction of 1.3 billion euros. Should this prediction come to pass, it will also represent about a 20% decline in profits from last year's 1.45 billion-euro record haul.

Three Ryanair jets parked on the tarmac

Ryanair stock was grounded on Monday. Image source: Ryanair.

Now what

And even that may not be the worst news. Ryanair told Reuters it " [can] not rule out further disruption," which could impact results and cause earnings to fall even more this year.

On top of that, rising oil prices -- a factor out of Ryanair's control -- are expected to reduce Ryanair's profits next year as well. Next year is fiscal 2020 for the Irish airline, and profits could fall by 3.5% for every 1% rise in the cost of jet fuel, according to London-based Goodbody Stockbrokers.

Little wonder investors are heading for the exits.

Rich Smith has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.