Lockheed Martin has resumed acceptance flights of newly built F-35 fighter jets following a three-month hiatus caused by engine problems, which first emerged in dramatic footage shared online.
The company announced on Monday that the first new acceptance flight had taken off from Fort Worth, Texas, the main place where F-35 fighters are manufactured, Defense News reported.
Acceptance flights are required before new F-35s can be delivered to the government. Lockheed halted the flights after an incident during an F-35B fighter’s quality check flight on Dec. 15.
The odd crash on a Texas runway was made public in footage that circulated online. The aircraft appears to hover over a runway, bounce off the ground, nosedive, and spin on the ground before the pilot safely ejects.
Deliveries of the F135 engine, made by Pratt & Whitney, were halted after an investigation found possible problems in that component. Investigators eventually discovered vibration issues in the engine, which a Pratt & Whitney official described as “a rare systems phenomenon involving harmonic resonance,” Defense News reported.
Still, the entire F-35 fleet worldwide was ordered to undergo a fix after a solution was found in February. The F-35 Joint Program Office said few aircraft had the vibration problem, but the fix was inexpensive and efficient enough to apply for consistency.
Though acceptance flights have resumed, it is not clear when F-35 deliveries to the U.S. government will be back on track.
“Safety remains our top priority,” Lockheed stated. “We will deliver the aircraft as quickly as possible after undertaking the multiple checks and test flights needed.”
The F-35 program has long been troubled by technical, financial, and logistical issues. Delays and cost overruns have made it the most expensive weapons program in history at an estimated $1.7 trillion over the fleet’s lifetime.
More than 890 of the aircraft have been delivered worldwide, with the F-35 now being flown by at least 17 countries, according to a Lockheed Martin fact sheet.