In an open letter to the company's CEO, the union said easyJet was stuck in an "infernal spiral" which put both crew and passengers at risk.
They said that managers were scheduling 'unrealistic' flight plans, asking pilots to do more flights than logistically possible - even to the point of exceeding legal safety limits.
And some pilots who refused to go beyond these limits were subject to "intimidation" from management in the UK's Luton airport, the letter said.
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One of the reasons pilots are being put under pressure, the letter states, is the fact that passengers are increasingly aware of their rights to claim compensation following delayed or cancelled flights. As a result, they wrote that "the employee is reduced to a cost, and the passenger to a profit".
But the union said this strategy was counter-intuitive, with the demands placed on pilots making flight disruption more likely.
In the past, most cases of flight disruption were said by the company's communications department to be due to to bad weather conditions, air traffic control strikes, or even Brexit, the letter stated. This year, however, the union said "serious structural dysfunction" was to blame.
In addition to problems of extreme fatigue, easyJet employees had also suffered from repeated payroll errors, with the union forced to help recover more than € 500,000 in arrears for France-based staff, it said.
The letter appealed to the founder of the company, Stelios Haji-Ioannou, to address the situation and work with managers to "restore the company values".
"Like you, we love this business you have created, and every day we put everything into it," the union wrote. But it added: "Our current management does not allow us to carry out our business in a calm and acceptable environment, in terms of security."