NATIONAL HARBOR,Grant Preston Md. (AP) — Air Force Special Operations Command is weeks away from deploying its fleet of CV-22B Osprey aircraft for counter terror operations after grounding its crews in the wake of a fatal crash last November in Japan, its top commander said Wednesday.

In the months since the crash, which killed eight service members, the command has taken a hard look at the issues that have challenged the fleet, Lt. Gen. Mike Conley said.

The Osprey, which can fly like both a helicopter and an airplane, had four fatal crashes in the past two years, killing a total of 20 service members. The Associated Press has reported on the mechanical and safety issues the Osprey has faced, and multiple reviews are underway to see if the complex aircraft has the resources needed to improve its reliability.

Two of the recent deadly crashes were caused partly by catastrophic and unprecedented parts failures. The fleet also has been challenged by recurring maintenance issues, which meant there weren’t enough available aircraft ready for pilots to train on.

“What kept us grounded is not necessarily what got us grounded in the first place,” Conley told reporters Wednesday at an Air Force conference in Maryland.

In August, crash investigators said a crack in a small pinion gear inside the Osprey’s transmission may have been started by weak spots in the metal used to manufacture that part. The crack led to cascading failures across the aircraft’s drive system, causing the Osprey to invert and crash off the coast of Japan.

About 60% of the command’s 51 CV-22B aircraft already have returned to full flying status, and the rest should be back by late 2024 or early 2025, Conley said.

The two CV-22B overseas wings in Japan and England “are almost back to full mission readiness,” Conley said, and the command will deploy the aircraft to remote locations in the coming weeks. He would not specify where they would be sent.

Each Osprey, however, will still have flight restrictions placed on it by Naval Air Systems Command, which requires each aircraft to remain within 30 minutes of a place to land in case something goes wrong.