EasyJet chief executive Andy Harrison is intending to step down from his post at the end of June next year.
Earlier this year the UK budget airline secured a retention agreement to keep Harrison in the role at least during the first quarter of 2010.
But Harrison says that, while he has "loved being part of EasyJet's success", he is "now looking forward to moving on to a new challenge".
EasyJet has not identified a successor but says the retention agreement with Harrison has been amended to ensure a smooth transition.
From 1 January 2010, the carrier adds, Sir Michael Rake will take over as group chairman, succeeding Sir David Michels.