Ryanair disclosed late on 6 October the resignation of its chief operations officer Michael Hickey, who will leave the Irish carrier at the end of the month.
The airline has faced significant adverse publicity in recent weeks after cancelling hundreds of flights and rowing back on expansion plans amid rostering issues relating to pilots.
Hickey is the first senior executive at Ryanair to resign since the scale of the flightcrew staffing issues became apparent.
Speaking to FlightGlobal in 2015 on the challenges of running a large, dispersed airline with dozens of bases, Hickey insisted that "we don't have independent republics", with Dublin overseeing all operations.
Hickey moved into the post in late 2013, having previously served as director of engineering at the carrier.
Reflecting on Hickey's departure, Ryanair chief executive Michael O'Leary states: "He will be a hard act to replace, which is why we are grateful he has agreed to continue in an advisory role to smooth the transition to a successor and to complete a number of large projects he is currently working on."
Ryanair has commenced the process of recruiting a successor.