What the Pentagon giveth, the Pentagon withholdeth, at least when it comes to the F-35.

The Defense Department is holding back $25.7 million from engine manufacturer Pratt & Whitney until the company improves its mechanisms for tracking costs and performance levels, according to Breaking Defense. The amount withheld represents about 5 percent of engine payments slated for Pratt & Whitney, a unit of United Technologies Corp.

Related: DOD Is Stuck with a Flawed $1.5 Trillion Fighter Jet

During congressional testimony yesterday, the head of the F-35 program noted some positive advancements by the engine-maker, saying it has increased delivery rates and even provided some engines ahead of schedule.

“However, far too often engine deliveries are interrupted by technical issues and manufacturing quality escapes resulting in product holds and material deficiencies that increase overall risk to meeting future production goals,” Lt. Gen. Christopher Bogdan told the Senate Armed Services Airland Subcommittee. “My production and quality teams continue to work closely with Pratt & Whitney to resolve the systemic issues which result in these product holds,” he said.

The F-35 Joint Strike Fighter is the Pentagon’s most expensive weapons program, costing an estimated $391.2 billion for development and production. The total cost over the lifetime of the program is estimated at $1.5 trillion.

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