The US Army issued an aviation stand-down after two helicopter accidents claimed 12 lives in recent weeks.

Following a series of fatal helicopter crashes in recent weeks, the US Army temporarily grounded all its pilots last Friday until they complete additional training to prevent future incidents and ensure the safety of its personnel. The most recent being the two AH-64 Apache helicopters colliding mid-flight in a remote area of Alaska on April 28 and two Black Hawk medical evacuation choppers crashing during a nighttime training mission in Kentucky last month.

In a press release, General James McConville said to have ordered a force-wide stand-down for the Army’s Aviation units “except those participating in critical missions, until they complete the required training.”

The grounding will also include aircraft overseas deployed in Europe and combat zones such as Iraq and Syria., however, reported that a two-star general or above can disregard the stand-down in emergencies such as medivac missions.

“During the stand down, the Army will review the risk approval/risk management process, aviation maintenance training program, aircrew training standardization and management, and supervisory responsibility,” McConville added, stressing that the safety of the pilots is the service’s top priority.

The statement also noted that active-duty units must complete the 24-hour orientation on safety issues between May 1 and 5, while National Guard and Reserve units have until May 31. Once completed, aviation units will be allowed to resume flight activities.

The Latest Deadly Mishap in Alaska and More

The recent Apache helicopter incident near For Wainwright, Alaska, was the last straw that prompted the Army to issue the stand-down order.

Two AH-64s collided mid-flight last Thursday, killing three soldiers and injuring another. Among the casualties, two were declared dead at the scene, while the third soldier died en route to the hospital. The crew, which was returning from a training mission, belonged to the 11th Airborne Division.