The commander of Marines in Japan has temporarily suspended flight operations for MV-22B Ospreys after an Osprey crashed Tuesday off Okinawa.

Lt. Gen. Lawrence Nicholson said that Osprey flights will resume when he is “satisfied that we have reviewed our checklists and safety of flight procedures,” according to III Marine Expeditionary Force.

Tuesday’s crash was the sixth major Marine aviation mishap since October. It came only six days after Marine Capt. Jake Frederick was killed when his F/A-18C Hornet crashed into the Pacific about 120 miles southeast of Iwakuni, Japan.

All five Marines aboard the MV-22B were rescued Tuesday by the Air Force’s 33rd Rescue Squadron after their Osprey crashed in shallow waters to avoid coming down over populated areas of Okinawa, a III MEF news release says. Two Marines remain hospitalized at the Camp Foster naval hospital.

Speaking at a news conference Wednesday in Okinawa, Nicholson said the MV-22B had been refueling midair when the Osprey’s rotor struck the refueling line, causing damage to the aircraft, according to the news release.

“After the aircraft was unhooking, it was shaking violently,” Nicholson said. “The pilot made a decision to not fly over Okinawan homes and families. He made a conscious decision to try to reach Camp Schwab and land in the shallow water to protect his crew and the people of Okinawa.”

Nicholson thanked the Japanese coast guard, the Okinawan police and the U.S. Air Force for their help, the news release said. He also sought to reassure Okinawans who are worried whether MV-22B Ospreys are safe.

“I regret that this incident took place,” Nicholson said. “We are thankful for all the thoughts and prayers the people of Okinawa gave to our injured crew.”

The Marine Corps is in the throes of an aviation readiness crisis brought on by years of war, budget cuts that delayed maintenance and delays in the F-35 program. The Pentagon’s internal watchdog is conducting an audit to see if the Corps has enough flyable aircraft and proficiently pilots.

“Our aviation readiness is really my No. 1 concern,” Commandant of the Marine Corps Gen. Robert Neller told Congress in March. “We don’t have enough airplanes that we would call ‘ready basic aircraft.’ That means we’re not getting enough flight hours.”

In late April, only 87 of the Marine Corps’ fleet of 276 F/A-18 Hornets were flyable, prompting the service to announce two months later that it was pulling 23 F/A-18s from storage and getting another seven from the Navy.

One reason the service is having so many problems keeping enough Hornets flying is that it decided to “skip a generation of fighter aircraft” by transitioning to the F-35 without buying any F/A-18 E-F Super Hornets as a stopgap measure, Jesse Sloman, an analyst with the Center for Strategic and Budgetary Assessments think tank in Washington, said in June.

The Marine Corps readiness recovery plan calls for having 162 flyable Hornets by mid-2017 or early 2018, Lt. Gen. Jon Davis, deputy commandant for aviation, told Marine Corps Times in September.

By July 2019, the Marine Corps hopes to have 589 of its 1,065 fixed- and rotary-wing aircraft, Davis said in an interview.

“Our readiness numbers are ticking up, but they are still shy of what they should be,” Davis said. “We’re not satisfied at all. We have a ways to go before we achieve full readiness recovery.”