Finland will order 64 F-35A multi-role fighter jets from US contractor Lockheed Martin to replace its ageing fleet in a massive deal worth 8.4 billion euros ($9.5 billion), the government said Friday.

Lockheed Martin defeated rival bids from Boeing, France's Dassault, Saab of Sweden and the Eurofighter consortium of the UK, Germany, Italy and Spain -- months after Switzerland picked the US planes.

It is Finland's biggest ever arms deal.

"The F35 fulfilled the demands for preparedness, industrial cooperation and cost," Defence Minister Antti Kaikkonen told a press conference.

"In comparisons of the military capabilities, the F35 overall system was the best at meeting our needs," he said, citing the plane's "battle, intelligence and resilience capabilities".

Lockheed Martin rivals expressed disappointment.

"Once again we notice and regret an American preference prevailing in Europe," Dassault Aviation said in a statement.

Sweden's defence minister Peter Hultqvist also voiced "regret" at the decision.

The deal will include AMIRAAM and Sidewinder air-to-air missiles, as well as spare parts, training solutions and maintenance until the end of 2030, the government said in a statement.

After a six-year tendering process, during which the planes were tested for their ability to operate in Arctic conditions, the Finnish defence forces will replace its existing fleet of F/A-18 Hornets by 2030.

The total costs of the procurement and infrastructure improvements will reach around 10 billion euros.

The first F-35s will be delivered to Finland in 2026 with the fleet of Hornets to be fully replaced by 2030,the government said.

Regional tensions

Finland's choice of the F-35 comes against a background of tensions between Russia and NATO, the US and Europe.

Moscow denies Western accusations that it is amassing troops on the Ukrainian border in preparation for a potential military operation.

Following Russia's annexation of Crimea in 2014, Finland repeatedly scrambled its Hornet fighters in response to a spike in incursions into its airspace by Russian jets.

The Nordic nation, which shares the EU's longest land border with Russia, is not a member of NATO but has increased its cooperation with the military alliance in recent years.

The F-35 fighters are expected to remain in service until the 2060s.

The government has budgeted a further 10 billion euros to the maintenance and upgrade costs of the jets.

But some commentators have accused Finland of over-optimism about the life cycle costs of the F-35A.

Critics point out that the government's annual maintenance budget of 254 million euros was less than half what Switzerland will spend per plane for its own recent order of F-35s.

However, the government said on Friday that the upkeep of the fleet was "feasible" and that the annual costs "will fall below" 254 million a year.