U.S. officials said on Wednesday they were nearing a fix for the engine that powers Lockheed Martin Corp’s (LMT.N) F-35 fighter jet and the United Technologies Corp (UTX.N) unit that makes the engine has agreed to pay to retrofit 156 already delivered.

Pentagon chief arms buyer Frank Kendall told reporters that the U.S. military was close to determining the root cause of a major engine failure in June, and test fixtures were being set up to ensure that Pratt’s proposed corrective actions were acceptable and adequate.

The failure of Pratt & Whitney’s F135 engine grounded the entire F-35 fleet for several weeks this summer and prevented the newest and most advanced U.S. warplane from making its international debut at two UK air shows. Flights have resumed but with certain restrictions on speed and other maneuvers. […]