A pilot assigned to the 58th Fighter Squadron, Eglin Air Force Base, Florida, performs a pre-flight checklist onboard an F-35A Lightning II aircraft at MacDill Air Force Base, Florida, Feb. 13, 2023. U.S. Air Force photo by Airman 1st Class Zachary Foster 

Defense News: Lockheed Martin resumes F-35 flights with engine vibration fix in hand 

WASHINGTON — Lockheed Martin on Monday morning resumed conducting acceptance flights of newly built F-35 Joint Strike Fighters, nearly three months after an engine problem grounded new jets and halted deliveries.

Lockheed announced Monday that the first flight took off from Fort Worth, Texas, where it builds the majority of F-35 fighters. 

“We resumed F-35 production flight operations today following an F135 engine mitigation action,” Lockheed Martin said in its statement. Lockheed stopped acceptance flights after a Dec. 15 mishap involving an F-35B fighter that was undergoing a quality check flight. 

A video showed the fighter bouncing on the ground, tipping forward and spinning before the pilot safely ejected. 

The investigation that ensued found signs of a problem with the fighter’s Pratt & Whitney-made F135 engine, and engine deliveries were halted in late December. Further investigation found the engine had vibration issues.  

Read more …. 

 Lockheed Martin Clears Crucial Hurdle To Restart F-35 Deliveries  

Lockheed Martin Clears Crucial Hurdle to Restarting F-35 Deliveries — Air Force Magazine

Lockheed resumes F-35 flights following December crash caused by ‘harmonic resonance’ — Flight Global   

New F-35s Are Being Test-Flown Again Following Texas Crash — Military.com