Aer Lingus intends to transfer a Heathrow slot pair to British Airways.
The summer-only overnight slot pair - a 22.00 arrival and 06.50 departure - is "surplus to the airline's requirements", wrote Aer Lingus company secretary and legal counsel Méabh Gallagher in a 23 April letter to shareholders.
EU slot regulations stipulate that the pair must be operated for summer 2013 or returned to the pool, under an 80/20 use-it-or-lose-it rule.
"Aer Lingus already has slots which closely coincide with these times," says Gallagher. "There is no commercial requirement for additional capacity at these timings and frequencies."
Noting that slots may not be sold but may be exchanged one for one, Aer Lingus proposes that it will "transfer its interest in the surplus slot pair to British Airways on a permanent basis for agreed consideration".
The Irish government and Ryanair - as shareholders each holding at least 20% of Aer Lingus's ordinary shares - can within 28 days of the notification request an extraordinary general meeting.