"What I find unjustified is that the pilots draw the short straw, because people want to fly cheaply", said Daniel Flamman, one of several passengers Reuters spoke to at Frankfurt airport who said they sympathised with the pilots.
But Ryanair, in a statement said "there will be no cancellations (of flights to and from the Netherlands) as a result of the unnecessary strike action by the Dutch pilot union".
Germany will be worst hit, with 250 cancellations at ten airports after the country's Cockpit union called on pilots towalk out from 3.01am local time (2.01am BST).
The company calls the strikes "regrettable and unjustified".
"They tweeted: "£ryanair cancelled my flight in the last min because of pilots strike.
Belgium-based Ryanair pilots gather at Charleroi Airport as part of a European-wide strike.
The Irish airline, Europe's largest low-priced carrier, averted widespread strikes before Christmas by agreeing to recognise unions for the first time in its 30-year history.
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But pilots counter that Ryanair has refused to engage in meaningful dialogue about collective labour agreements since it began recognising unions in December 2017.
French news source France Info dubbed the strike "historic", specifying that it is the biggest walkout in the history of Ryanair.
The action is the largest in a series of strikes over pay and conditions.
The unions are demanding a raise in salaries, unions say, alongside the issuing of more secure working contracts that are valid in each pilot's country of residence (which they claim does not always happen).
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But its combative chief executive Michael O'Leary has also warned the airline may shift jobs and planes to more profitable areas if the turmoil continues.
That was because the strikes were hurting bookings, Ryanair said, and although it was too early to assess the impact elsewhere, it added that the action will hit average fares from having to move customers to flights it could otherwise have sold at a high last-minute price.
Responding to the comments Mr Calder made on the BBC today, Ryanair told Express.co.uk: "In the case of a cancelled flight, if the customer requests a full refund, then no further compensation is due".