The F-35 Lightning II is one of the most expensive weapons program ever and has been plagued with cost overruns and delays since it launched. New details on the generator failure that caused an emergency landing and the subsequent grounding of the F-35 fleet have been unveiled.

Defense News reports that the generator failure that affected test aircraft AF-4 has been determined to be the result of an improper maintenance technique that goes along with a new generator layout in some of the newer F-35 fighters. Once the problem was traced to the new generator layout in newer aircraft, the F-35s using the older generator layout were cleared to resume flight operations.

The earlier aircraft that resumed flight operations included three F-35As and four F-35Bs. Defense News reports that the maintenance procedure has now been revised and that the full fleet of F-35s are now back to operation.  The aircraft with the older generator layout resumed flights on March 14. The cause of the generator failure in the test aircraft was traced back to an excess of oil inside the generator.

The excess oil circulation inside the generator after maintenance caused the generator to overheat and fail. Lockheed claims that the loss of flight time has not impacted the test flight schedule. The F-35 program is still ahead of its flight schedule for the month.

The F-35's have taken back to the air, but AMD Online reports that the second power plant for the F-35 has officially been killed. We reported in February that the House was set to vote on the bill to kill the second engine.

The stop work order was announced last Thursday. GE Aviation in Ohio was developing the second engine.