Oneworld alliance member British Airways is to acquire six slot pairs at London Heathrow from struggling Lufthansa Group carrier BMI.
The six slots are for daily operations and BA's parent company, IAG, said the carrier would put them into use from late October.
BA is looking to "expand both its long-haul and short-haul network at the airport", IAG added.
While Lufthansa Group had previously indicated that it could lease BMI slots at Heathrow to other carriers, to help cut BMI's losses, BA stresses that the acquisition is a "purchase".
"It's permanent," said a spokesman for the carrier.
No details have been disclosed about the transaction price, and BA is yet to finalise the routes to which the slots will be allocated.
The agreement raises BA's slot share at Heathrow by around one point to 43.9%.
Lufthansa Group has previously traded BMI slots within Star Alliance to help prop up the loss-making UK operator's financial position.