The Pentagon’s decision to move into production of the F-35 Joint Strike Fighter before it had been adequately tested was a crucial mistake that is still taking a toll on the most expensive program in the building’s history, the acting undersecretary for acquisition said yesterday.

“Putting the F-35 into production years before the first test flight was acquisition malpractice,” Frank Kendall, who has been nominated to permanently takeover the post, said during a speaking appearance. “It should not have been done.”

Overly optimistic predictions based on design tools, simulations and modeling led to the false assumptions that the Lockheed Martin [LMT]-built aircraft would not encounter serious problems when it reached flight testing, Kendall said.

“Now we are paying the price for being wrong about that,” he said.

The Pentagon plans to buy 2,443 F-35s for the Air Force, Navy and Marine Corps for a price tag now estimated at $383 billion. The program has faced massive cost overruns, technical problems and delays that have brought about sharp criticism and some calls for cancellation.

Defense Secretary Leon Panetta in January announced plans to slow production of the F-35 over the next several years to give more time to work out the problems and to reduce costs at a time of declining defense spending. The Pentagon has nevertheless remained steadfastly behind the next generation multi-role stealth fighter.

“All those aircraft are making progress and we’re committed to the program,” Kendall said. He said the program has completed 20 percent of required tests and that number should rise by about 15 to 20 percent in each of the coming years.

Speaking at the Center for Strategic & International Studies, Kendall outlined his priorities for the office if confirmed by the Senate to become the next undersecretary for acquisition, technology and logistics. He has been acting in that capacity since the end of October. The Senate Armed Service Committee has not announced a hearing date but it is expected to take place in the next few months.

The F-35 is just one example of the shortcomings in major acquisition programs in recent memory that must change, Kendall said. Officials need to get a better handle on the cost of a program to determine whether it is affordable and realistic before it gains steam.

He pointed to the Air Force’s F-22 fighter, the Navy’s Zumwalt-class (DDG-1000) destroyer and the Army’s Future Combat Systems as programs that went too far into development before it was understood they were too costly and had to be either canceled or scaled back. Better analyses of cost and execution need to be implemented.

“We will not have programs like that," Kendall said. "And the best way to stop them is before they start.”

The Pentagon will move more toward systems that do not take years to develop but instead can be relatively quickly fielded and tested, and meet cost goals, he said.

Kendall said he will pursue more comprehensive tools for evaluating program performance and institutionalizing knowledge of past programs to promote best practices and to avoid repeating mistakes.