The Air Force and Navy said Friday that some of their F-35 Lightning IIs are once again flying, a day after the military grounded the entire fleet of its most advanced fighters.

The Pentagon’s move Thursday came just days after a U.S. Marine Corps F-35B crashed in South Carolina. Investigators feared the crash was caused by a problem with the F-35′s fuel tube, which led to the fleet-wide grounding and inspection of fuel tubes within the engines of all the stealth fighters.

Air Force spokeswoman Laura McAndrews said in an email that the majority of the Air Force’s F-35As have been inspected and returned to flying status. Some F-35s — though the Air Force did not say how many — still require additional maintenance, however. McAndrews said the Air Force is working with the F-35 Joint Program Office to solve that problem as quickly as possible.

Navy Capt. Max “Pepper” McCoy, the commodore of the Navy’s Joint Strike Fighter Wing, said in a statement that the Navy is carrying out a flight schedule with F-35Cs that have completed and passed the inspection. McCoy also said that his wing will continue fleet-wide inspections of its F-35Cs.

“We continue to balance safety with operational requirements,” McCoy said. “Safety is our primary goal, and we will continue to take every measure to ensure safe operations while we continue to execute our mission.”

The Marine Corps said the 13th Marine Expeditionary Unit and all three of its active air wings have resumed normal F-35 flight operations.

The Joint Program Office, in its statement Thursday, said it expected to finish inspections within 24 to 48 hours.

Navy Times editor Carl Prine and Marine Corps Times reporter Shawn Snow contributed to this report.