A rash of non-combat helicopter crashes has killed more soldiers since Oct. 1 than died in similar accidents in the previous two fiscal years combined, which prompted the five-day safety stand down of 1,000 aircraft that ended Dec. 7.

Army Forces Command chief Gen. Robert Abrams made the call to ground all helicopters and UAVs owned by FORSCOM in the United States until close of business Dec. 7. The five-day stand down that began Dec. 3 affected 11 Army bases and about 1,000 aircraft, including AH-64 Apaches, CH-47 Chinooks and UH-60 Black Hawks. The stand down did not apply to aircraft belonging to other commands or to those overseas.

“We cannot allow tragedy to pass unacknowledged,” Abrams said in a statement. “We must do whatever is needed to make certain that our Soldiers are training and operating safely.”

FORSCOM and Army aviation officials used the five-day break in flying to reevaluate flight-safety procedures before and during training exercises. The stand down was sparked by concerns over safety, training and maintenance procedures, not concerns over mechanical issues with the aircraft. Army investigators have not determined the cause of the recent crashes.

The official orders called for leaders in FORSCOM to “review Army aviation training procedures and helicopter-safety precautions to manage risk and to avoid accidental loss of aviation personnel and equipment.

“My decision to ground our aircraft today is taken with the utmost seriousness and my responsibility as the Commander of U.S. Army Forces Command,” Abrams said.  “I have a duty to ensure that we are doing all that we can to prevent loss of life and aviation accidents, and that is why we’re standing down to review our procedures and reaffirm our commitment to operating our aircraft safely and effectively.  Our thoughts and prayers are with the families of the Soldiers who died recently in these accidents.”

Army aviation leaders under FORSCOM were directed to review the flight-mission briefing process, paying particular attention to minimizing risk, crew selection, flight planning and pre-flight briefings, debriefings and after-action reviews.

Officials also went over the Army’s aircraft coordination training, adherence to flight operations standards, planning for accidents and individual units’ maintenance training, procedures and supervisory responsibilities, according to FORSCOM.

Investigations into the recent fatal crashes are ongoing at the unit level. Specific causes and circumstances of those accidents are pending review by the units involved and by the U.S. Army Combat Readiness Center, FORSCOM said.

Fourteen accidents have killed eight Army aviation personnel since the fiscal year began Oct. 1, according to Army accident statistics current as of Dec. 3. Sixteen total accidents occurred in fiscal 2015 and 18 in fiscal 2014, but only two soldiers were killed in 2015 and none the previous year, the statistics show.

The first accident in the current fiscal year occurred Nov. 23 when an Apache crashed in South Korea during a routine training mission. Two soldiers died in that incident.

A Black Hawk went down the same day at Fort Hood, Texas, killing four soldiers. Two more soldiers were killed Dec. 2 when another Apache crashed near Fort Campbell, Ky.