"All first wave flights to and from UK airports departed as scheduled this morning, with 97 percent punctuality," Ryanair said in a statement, adding that the minimal disruption was due to air traffic control delays.
"We do not expect any disruptions to our flights to/from our UK airports today," it added.
Meanwhile in Portugal, the only delay was to a flight from Porto to Milan, which was put back until the afternoon.
Pilots in Britain were striking Thursday and Friday, while cabin crew in Portugal were on their second day of a five-day walkout.
Ryanair's Britain-based pilots won permission late Wednesday to strike following a ruling by London's High Court after the Irish carrier demanded it be blocked.
However the High Court in Dublin has prevented Ireland-based pilots from joining the walkout.
In Portugal, disruption has been limited after the country's government ordered workers to deliver at least a minimum service.
Ryanair cabin crew in Spain have called for ten days of strikes in September.
The minimal fallout from the strikes contrasts to last year when pan-European stoppages affected thousands of passengers - and led to Ryanair offering improved pay to staff via landmark deals with unions. But Irish union Forsa claims its 2018 agreement was limited to matters of the time only.
Ryanair claims Forsa has not outlined specific pay demands, has been hasty in their movement to strike and conducted the strike ballot improperly.
The strikes come as the Dublin-based carrier faces several headwinds that are cutting into its growth and profits.