The Pentagon’s five-year budget plan for the F-35 falls short by as much as $10 billion, the military’s independent cost analysis unit has concluded, a new indication that the complex fighter jet may be too costly to operate and maintain according to Bloomberg News.

The Defence Department’s blueprint for the next five fiscal years calls for requesting $78 billion for research and development, jet procurement, operations and maintenance and military construction dedicated to the F-35 built by Lockheed Martin Corp. But the cost analysis unit estimates $88 billion will be needed.

The estimated shortfall was set out in a four-page review dated June 17 and marked “For Official Use Only.” The document, obtained by Bloomberg News, provides the first comprehensive estimate through 2077 for the Pentagon’s costliest weapons program since it underwent a major reorganization in 2012.

The F-35’s total “life cycle” cost is estimated at $1.727 trillion in current dollars. Of that, $1.266 trillion is for operations and support of the advanced plane that’s a flying supercomputer.

“As the five-years numbers are estimates, we do not have a reaction,” said Brandi Schiff, a spokeswoman for the Defence Department’s F-35 program office.