Ryanair pilots at the airline's Madrid base have overwhelmingly rejected the company's offer of pay rises of up to 22% aimed at addressing recruitment and retention difficulties.
The offer was conditional on pilots continuing to negotiate solely through local Employee Representative Committees at individual bases, rather than through unions, or through their new joint in-house European Employee Representative Committee.
The airline has recently been forced to cancel more than 20,000 flights due to mismanagement of pilots' annual leave and shortages of pilots, with at least 140 recently defecting to rival Norwegian Air alone.
The cancellations affected more than 700,000 passengers.
Ryanair had given the pilots in Madrid until this Friday to complete a ballot on the pay offer presented to their local ERC.
However, according to two sources, the pilots rejected the proposals by 80.88% to 19.12%.
The proposals would have delivered significant pay rises of up to €12,000 per year for captains, and €6,000 for first officers along with other incentives, including an unspecified number of additional contracts of direct employment.
Many pilots believe that Ryanair's current negotiating system places them at a disadvantage because it fragments their bargaining power with the airline.
They are also concerned about Ryanair's employment model, whereby many pilots are employed through agencies or special companies, rather than through contracts of direct employment.
Apart from demanding improved employment contracts, the pilots want Ryanair to negotiate with them through their joint EERC, something that CEO Michael O'Leary has categorically ruled out.
The Madrid offer also specified that any new contracts would not change the fact that crews would continue to be employed on Irish contracts of employment, or that Irish law would continue to be applicable to any amended contracts.
Asked about the Madrid outcome, Ryanair said it did not comment on "rumour or speculation".
The result of the ballot at Stansted - one of Ryanair's biggest bases, where a similar offer is on the table - is awaited by Friday.