Finland’s Air force began testing candidate aircraft vying to replace the Air Force’s aging fleet of fighter jets on Thursday, as the government weighs a purchasing decision due next year.

Each of the five short-listed manufacturers will bring their aircraft to Finland for a week of flight tests at the Satakunta Air Command in Pirkkala, in the Tampere region. The field tests will run until the end of February.

The first fighter jet up for assessment is the Eurofighter Typhoon, followed by Lockheed Martin’s multi-purpose F-35 combat aircraft and Boeing’s F/A 18 Super Hornet.

French firm Dassault’s Rafale and Swedish Saab’s Gripen E round out the contenders to replace the fleet of fighter jets.

Finland has sent all five manufacturers follow-up invitations to tender bids to completely replace the current Hornet fleet. Their responses are expected by the end of January.

A final binding invitation to tender will be sent out later this year and the government will make a purchasing decision in 2021. The aim is to commission the new fleet between 2025 and 2030.

The total estimated cost of the acquisition has been pegged at between seven and 10 billion euros, excluding lifetime costs such as spare parts and maintenance.

The original Hornet fleet was purchased in 1992 and will be phased out by 2025.