Several adjustments related to the F-35 Joint Strike Fighter program could make the plane more expensive for European buyers.

Rolls-Royce and General Electric earlier this week announced they would make adjustments to an alternate engine for the Lockheed Martin fighter plane, possibly resulting in additional development costs. The companies decided to redesign the engine after malfunctions during testing.

The primary engine for the F-35 is being built by Pratt & Whitney, a daughter company of United Technologies. Washington has green-lighted funding for an alternate engine to boost the plane's flexibility and its performance in high-altitude fighting.

And even if the redesigned engine has no effect on costs, the program will still require additional billions and more time, experts say.

"A new assessment of the Joint Strike Fighter program affirms earlier findings that substantially more money and time are required for the Pentagon's largest acquisition effort, a conclusion that could pose a formidable test of Defense Secretary Robert Gates' recent support for the F-35 program and President Barack Obama's pledge to terminate weapons with bloated price tags," InsideDefense.com reports.

Apart from the U.S. military, which plans to buy nearly 2,500 F-35s, several hundred additional planes will be sold to Canada and Australia as well as a host of European nations including Britain, Italy, Denmark, Netherlands, Turkey and Norway.

The latter may see additional costs to its F-35 program.

According to Defensenews.com, the Norwegian town of Bodo wants to relocate a key air base because of fears that takeoff noise levels of the F-35 could be significantly higher than those of the F-16, the Norwegian air force's current plane of choice.

"We are looking for a solution to what could become a significant noise problem for Bodo town once the F-35s arrive here," Odd Tore Fygle, Bodo's mayor, was quoted by Defensenews.com as saying. "The Air Force has had an air base in Bodo for 50 years, so we are used to living near a busy military air base. From what we know, the F-35s are more noisy than the F-16s based here at present, and this poses a problem for citizens and life generally in Bodo."

The F-35 is a fifth-generation, single-seat, single-engine, stealth-capable multi-role fighter that can perform close air support, tactical bombing and air defense missions. It is built by Lockheed Martin with Northrop Grumman Corp and Britain's BAE Systems as major partners.

The F-35 has three different models; one is the conventional takeoff and landing variant, the second is a short takeoff and vertical-landing variant, and the third is designed for carriers.