The director of the Army National Guard has ordered an aviation safety stand-down for all Army National Guard helicopter units, meaning helicopter units will stop flying to “review safety policies and procedures,” the National Guard announced Tuesday.

The stand-down went into effect on Monday following two helicopter crashes this month, the National Guard said. A National Guard official said the stand-down would be completed when the units finish their review.

“We are a combat force with helicopters training or on mission worldwide every day,” Lt. Gen. Jon Jensen, director of the Army National Guard, said in a news release. “Safety is always at the top of our minds. We will stand down to ensure all of our crews are prepared as well as possible for whatever they’re asked to do.”

The announcement comes just days after two Mississippi National Guardsmen — Chief Warrant Officer 4 Bryan Andrew Zemek and Chief Warrant Officer 4 Derek Joshua Abbott — were killed when their AH-64 Apache helicopter crashed during a training flight.

In a separate incident in Utah earlier this month, two pilots were injured but survived in a crash involving an AH-64D Apache helicopter.

The aviation stand-down comes as the US military is also in a fleet-wide V-22 Osprey stand-down following a deadly CV-22 crash off the coast of Yakushima Island, Japan, in December, which killed all eight airmen aboard. It also follows an Army-wide aviation stand-down last year after two deadly helicopter crashes, during which units were required to review safety and training protocols.

Asked Tuesday if Defense Secretary Lloyd Austin had concerns about the Army’s aviation program, Pentagon spokesman Maj. Gen. Pat Ryder said safety “is something that we’re always going to be concerned about and take seriously.”

“You will see senior leadership making safety a priority, as evidenced again by the fact that the National Guard Bureau recognizes hey, we need to take a moment here to stand down, review safety procedures and processes, and make sure we can look each other in the eye and go out there and do our mission safely,” Ryder said. “So the Secretary is confident in the service secretaries and chiefs and their leadership in terms of addressing addressing safety concerns.”