The US Army’s grounding of hundreds of AH-64E Apache attack helicopters could stay in place for months. An official told Military Times the pause would affect every squadron as the service runs a global inspection.

The Army announced the move on October 2. It ordered an “immediate, temporary pause in flight operations” for Apaches fitted with Improved Drive System transmissions. About 400 of the Army’s roughly 700 Apaches are affected. Every active-duty and National Guard Apache unit is included.

The decision followed technical and airworthiness reviews of the transmission. Earlier reports said the system could suffer an internal failure that cuts tail-rotor thrust, electrical power, and hydraulics. The root cause is still unclear.

This is the second safety grounding of the Apache fleet in two months. In August, the entire fleet was briefly grounded after an AH-64 from Fort Hood, Texas, crashed in a field on August 12, killing both pilots. That pause lasted just over a week. The Army says safety is its foremost priority and will share more details when appropriate.