All Ryanair flights to and from British and Irish airports departed without disruption, the airline said, as some of its British-based pilots began a 48-hour strike.
It added that it expected no impact for the rest of the day from a strike by some of its pilots based in Britain.
In a tweet, the airline thanked "all our UK pilots who have chosen to work to protect the flights and travel plans of our customers and their families over the bank holiday weekend".
Afternoon Update: pic.twitter.com/AyoVPTJoif— Ryanair (@Ryanair) August 22, 2019
Ryanair unions in Ireland, Britain, Spain and Portugal have been planning strikes over various grievances that began with a five-day cabin crew walkout in Portugal yesterday and continued with a 48-hour strike by some UK pilots today.
Europe's biggest low cost airlines said its first flights to and from UK airports today operated with 97% punctuality, with the slight slip due to air traffic control delays.
While more widespread strikes over pay and conditions a year ago forced Ryanair to cancel hundreds of flights, the airline has forecast minimal disprution this time and ran a full schedule without major delays in the first day of action in Portugal.
With the exception of two delayed flights, all departures from Portugal appeared to be operating as normal today.
Fernando Gandra, head of the SNPVAC trade union representing striking Portuguese cabin crew, told Reuters the airline hadmanaged the fallout by making major changes to departure times in advance and notifying passengers ahead of time.
Ryanair also limited the potential disruption by taking its fight to the courts and winning an Irish High Court injunction to prevent Dublin-based pilots striking.
A London court rejected a similar application against its British pilots, who plan a second strike from the early hours of September 2nd until just before midnight on September 4th.
Ryanair has said the striking pilots, members of the British Airline Pilots Association (BALPA), represent less than 30% of those operating its aircraft there.
Unions representing cabin crew in Spain said this week their plans for 10 days of strikes next month still stood after around of mediated talks with the airline ended without agreement.
The strikes are the first since Ryanair managed to quell last year's disputes by reaching pay deals with many staff in Europe following its dramatic U-turn in late 2017 to recognise trade unions for the first time.
However, it has failed to move beyond recognition deals with others and further angered unions by telling staff last month that it had 900 more pilots and crew than it needed due to delays in the delivery of the grounded Boeing 737 MAX, and would have to close some bases.