Ryanair is threatening to cut more flights to Spain as its row with the nation's airport operator continues. Aena recently confirmed its biggest increase in airport fees in a decade and Ryanair is now set to reduce the number of flights heading to Spain's regional airports.

The CEO of the budget airline, Michael O'Leary, has warned he will cut flights this winter season if the airport operator fails to reduce fees. It comes after Ryanair has already cut 12 routes this summer, including all operations at smaller airports such as Jerez and Valladolid. Routes have also been cut at Santiago de Compostela, Asturias, Cantabria, and Zaragoza.

As reported by The Local, Mr O'Leary said: "There will be significant cuts in Spain," adding: "Some regional airports will close this winter." However, Ryanair is increasing its number of flights to major Spanish airports such as Madrid, Alicante and Malaga.

Both Barcelona El Prat and Madrid's Barajas airports are set to benefit from billions of euros worth of investment over the coming years. It will be funded by fees that Aena charges airlines, but O'Leary claims the operator will "waste" money on "building facilities that airlines do not want or need as a way to increase fares."

He added: "We do need investment in Barcelona and Madrid but not for additional runways." The Ryanair boss claims the projects are a way of justifying fee increases.

Aena is proposing a 6.5% increase in the fees it charges airlines. This will be the largest since 2015, translating into an average increase of 68 cents per passenger.

Airport fees in Spain are decided by Aena and increased by over 4% last year due to inflation. Ryanair, who carried 200 million passengers across Europe last year, previously said they were not looking for "subsidies or special treatment".

However, they called for a model with competitive rates for all airlines. They argued that regional airports in Spain needed low costs to help stimulate growth.

Aena's president, Maurici Lucena, previously told shareholders: "Changing fares on a whim by Aena or due to spurious pressure from an airline would be a serious illegality."