In an open letter to prime minister Antonio Costa, the airline claimed TAP "cannot and will not" use the slots because of a reduction in its fleet. 

Ryanair chief Michael O’Leary said the airline would be able to maintain an additional three aircraft and deliver one million more passengers in Lisbon this summer if they were allocated the slots. 

However, O’Leary said the carrier will be forced to close 20 routes from Lisbon and relocate three aircraft away from Portugal this summer if no response was received by Saturday (5 March). He said the move could cost up to 150 jobs in Lisbon.

"At a time when Ryanair is investing heavily in Portugal, and in Portugal’s post-Covid recovery, we ask you to act in the best interest of Portuguese consumers, jobs and tourism," O’Leary wrote.

"Otherwise, these routes, these passengers, and these jobs will be lost this summer in Lisbon Portela." 

Ryanair said it previously wrote to Costa about the issue on 16 February and had not received a response to date (Friday, 4 March).