Britain was forced to ground all 16 of its new F-35 fighter jets after the United States government discovered that a faulty fuel tube was behind a crash last month.
"The aircraft mishap board is continuing its work and the US Marine Corps will provide additional information when it becomes available".
Inspections are expected to last a day or two, the department said.
Lockheed is slated to deliver 91 jets this year.
The inspections should be complete within 24 to 48 hours, Task & Purpose reported, citing a Pentagon official. If the aircraft has good fuel tubes, it will be allowed to begin flying again. During the subsequent investigation, certain fuel tubes were identified as a potential problem, largely involving aircraft built before 2015.
The announcement of the grounding comes after a United States Marine Corps F-35B from the 2nd Marine Aircraft Wing, Marine Fighter Attack Training Squadron 501, known as the "Warlords", crashed in SC near Marine Corps Air Station Beaufort on September 28.
"At this time, the cause of the mishap has not yet been determined", said Capt. Christopher Harrison, a U.S. Marine Corps spokesman.
Even before the F-35 grounding, experts speculated that Mattis's goal of reaching 80 percent readiness for these aircraft-the F-35, F-22, F-16, and F/A-18-was a pipe dream.
While the F-35's U.S-based Joint Program Office had indicated that the grounding included aircraft purchased by foreign militaries, the British military signaled Monday that its entire fleet is not grounded. "We will take every measure to ensure safe operations while we deliver, sustain and modernize the F-35 for the warfighter and our defense partners".
So far, the U.S. military has taken delivery of 245 F-35s, a lot of them to the Air Force. In May, Israel announced it had conducted the first combat missions ever using the F-35 but offered few details.
More than 320 F-35s around the world must now undergo the inspections, according to a source familiar with the program. The Israeli warplanes, purchased from the USA, are a different model than the American one that crashed.
For the U.S. Defense Department, the timing could not be worse.
It cost an estimated $400bn and had a goal to produce 2,500 aircraft in the coming years.
In a statement, the F-35 Joint Program Office said the U.S. and its global partners had suspended flight operations while a fleet-wide inspection of fuel tubes was conducted.
Because the problem is related to a fleetwide engine issue, rather than just in the F-35B models, it appears unlikely that the problem is unrelated to the short-takeoff and vertical-landing capabilities of the Marine's design.