For the second time in five weeks, the most advanced fighter jet in history has been grounded with mechanical problems.

For the second time in five weeks, the most advanced fighter jet in history has been grounded with mechanical problems.

The Department of Defense on Friday announced that the Air Force, Marine and Navy variants of the F-35 were grounded after a crack was discovered on the engine blade of an Air Force F-35A at Edwards Air Force Base in California.

Unlike the most recent nearly one-month flight suspension that affected just the F-35B Marine variant, all three variants were grounded Thursday.

“In this situation, the F135 engine, the core of the engine, is the same for all variants of the F-35,” said Col. Andrew Toth, commander of the 33rd Fighter Wing at Eglin Air Force Base, where pilots and maintainers train.

Toth said it was hard to speculate how long the F-35s would stay on the ground. A full analysis of the engine and the cracked blade is needed to determine the cause of the problem. The evaluation will be conducted at Pratt & Whitney’s Engine Facility in Middletown, Conn.

The crack was discovered during a routine inspection Tuesday, according a news release from the F-35 Joint Program Office.

Toth said maintainers conduct thorough borescope inspections of the engine and all of its blades before every 25 hours of engine time.

“As young as the system is as we’re going through, these types of things are expected to happen occasionally,” Toth said. “The great part about that is we have a great team here and at the Joint Program Office on down that looks at this stuff and makes sure we can continue safe and effective flying operations.”

This is the sixth time one or all variants of the F-35 have been grounded.

Lockheed Martin, the prime contractor for the F-35, released its own statement Friday.

“Lockheed Martin is fully engaged and working closely with the JPO and Pratt & Whitney to determine the root cause of the blade crack found during a routine inspection of an F135 engine on an F-35A at Edwards Air Force Base, Calif.,” the statement said. ”Safety is always our first consideration, and the joint inspection team is focused on ensuring the integrity of the engines across the entire fleet so the F-35s can safely return to flight as soon as possible.”

Eglin has 22 F-35s for the Air Force and Marines. The Navy’s F-35Cs are scheduled to arrive in April.

Toth said there will be plenty to keep pilots and maintainers busy while flights are suspended.

“The benefit about this is we can still conduct standard maintenance activity on the aircraft out there for the guys who are working on the flight line,” Toth said. “As far as maintenance goes, we can do our routine maintenance, continue to work on the aircraft. There will be no shortage of things for our maintainers to do.

“As far as the pilots go, another bonus here is we’ve got the simulators, and they’ll still be up and running,” he added. “So they’ll have an opportunity to go and maintain as much currency as possible and practice emergency procedures in the aim to improve their capabilities.”

Contact Daily News Business Editor Dusty Ricketts at 850-315-4448 or Follow him on Twitter @DustyRnwfdn.