Ryanair pilots will announce more strikes early next month, when their German colleagues may also mount pickets.
Sources revealed that August 2 and 10 will be given serious consideration as potential dates at a meeting of a Forsa disputes committee.
Strikes by cabin crew in Spain, Portugal and Belgium will hit up to 100,000 passengers as 600 flights are grounded over the next 48 hours.
Ryanair has not said whether Irish flights will be affected by this industrial action, but sources in the travel industry claimed only two outbound and two inbound Irish flights will be cancelled.
Meanwhile, German and Irish pilot unions are likely to be on strike during the first two weeks of August.
Members of German union Vereinigung Cockpit are currently balloting. Up to 2,500 passengers were hit yesterday during a third strike by Irish-based, directly-employed pilots, which led to 16 cancelled flights.
Ryanair said they make up 25pc of its pilot workforce. Most pilots are contractors.
So far, the airline has minimised the impact of the strikes by rebooking passengers on alternative flights or providing refunds, so there were no angry scenes at Dublin Airport.
Passengers who were asked by the Herald while checking in at the Ryanair desk said they had not been affected.
Pilots staged their picket outside Ryanair's HQ, in Airside, Swords, from early morning and they were joined by pilots from American Airlines in support while most cars beeped horns as they passed.
"It's industrial action, but not as we know it," quipped one observer about the pilots' upmarket picketing style.
The pilots want a seniority list to be set up that gives those with longest service first call on holidays, promotions and transfers, but the airline claimed it could not explain their demand, and said it "doesn't even affect them".
Ryanair chief operations officer, Peter Bellew, defended the airline against a claim made in a tweet that the airline had a "big alignment with the basics of 21st century slavery".
"I'm not sure how you define a pilot on €150,000 to €200,000 and attending work for 170 days a year as a slave," he replied.
Forsa spokesperson, Bernard Harbor, said further industrial action by pilots could not legally take place for another week, if it is announced today.
He said this could give both sides "breathing space" for talks.