Ryanair shares dipped slightly after its success in blocking a 48-hour strike by its Dublin-based pilots was followed by the British High Court giving the green-light for a potentially more damaging UK pilot strike.
Ryanair shares - already down around 20% since the turn of the year - initially rose as much as 2% on the Irish High Court ruling blocking this week's planned strike action of Irish-based pilots.
However, they closed down just over 1% after the airline failed in a legal bid to prevent a strike by pilots in its biggest market of the UK.
Britain's High Court refused to block the walkout, dismissing a request for a last-minute injunction against the action. The two-day walkout threatens services at London Stansted, Ryanair's largest hub.
Airline stocks have had a turbulent year. Ryanair's share price has fallen by over 36% in the past 12 months; UK rival EasyJet's by 39% and Aer Lingus and British Airways-owner IAG's by 33%.
Lufthansa has lost more than 40% of its share value in that time, with only Air France-KLM seeing an increase.
One analyst said while issues with trade unions are never helpful to investor sentiment, the actual final impact on flights and passenger movement is a more accurate barometer than the basic threat of industrial action.
Brexit is still outweighing strike threats as the main concern for airline investors, they said.
Ryanair has been battling the threat of strike action in Ireland, Britain, Portugal and Spain of late. Spanish cabin crew are threatening to strike in September, while their Portuguese counterparts have begun a five-day strike over holiday pay.
Ryanair said only a small number of fights from its Portuguese bases might be affected by minor schedule changes and that affected customers had been notified.
No delays or cancellations have been reported at Ryanair's bases at Lisbon, Oporto and Faro.
Ryanair said the UK strike only affects a minority of pilots and has pledged to operate a full schedule. Davy analyst Stephen Furlong said cancellations could be limited, though the airline may also suffer a longer-term impact on bookings.
-additional reporting Bloomberg and Reuters