Australia announced Tuesday it will buy 58 more F-35s at a cost of $12.4 billion to build their fleet of fifth generation fighters to 72.

The purchase agreement offered a boost to the Joint Strike Fighter program a week after it was announced the costs increased by $7.4 billion at a time the U.S. expect costs to drop.

Australia’s decision to stick to the plan and increase their planned buy beyond the 14 F-35s the Australians agreed to buy in 2009 offers hope to the Joint Strike Fighter. Earlier this year and in 2013, rumors have circled that countries like Denmark and Canada are looking at other options and possibly leaving the F-35 program.

If allies pull out of the program, the costs sky rocket as the Joint Strike Fighter program was always justified as a program that will benefit from the efficiency of scale. Without the scale of multiple countries buying the aircraft, the costs go up and more countries leave the program.

This summer should prove to be an important time for the F-35’s international portion of the program with the plan to fly the F-35 at the Farnborough Air Show outside London in July. This will be the first time the F-35 has flown outside the U.S.

Many assume the U.S. chose to show off the F-35 at Farnborough in order to boost confidence in the program and keep allies like Australia on board.

Of course there are others that say the U.S. got tired of watching Russian fighters last year at the Paris Air Show and plan to one up Vladimir Putin with the F-35.