WASHINGTON - The US Army on Sunday identified two soldiers killed in an Apache helicopter crash at Fort Campbell, state of Kentucky, on Friday.

The two soldiers, identified as Chief Warrant Officer 3 Ryan Connolly, 37, and Warrant Officer James Casadona, 28, died when their AH-64E Apache helicopter crashed during a routine training mission at Fort Campbell late Friday.

Connolly was an instructor and Casadona was a pilot in the 101st Airborne Division's combat aviation brigade, Army officials said in a news release.

"This is an unfortunate event, and we are saddened by the loss of our fellow soldiers," Colonel Craig Alia, the commander of the brigade, said in the release.

The cause of the accident is under investigation, the Army said.

The incident followed a series of mishaps involving US military aviation.

Four Marines died Tuesday in the crash of their CH-35E Super Stallion helicopter during a training flight in California. On the same day, a Marine jet went down at an airport in Djibouti, and the pilot was hospitalized after ejection.

A pilot of the air force's elite Thunderbird squad died Wednesday when his F-16 jet crashed near an air base outside Las Vegas as he was preparing for an air show.

Those crashes have led to a call in Congress for the Pentagon to scrutinize the military priority.

"The readiness of our military is at a crisis point," said Mac Thornberry, chairman of the House Armed Services Committee.

"There can be no higher priority for the Department of Defense than ensuring that our aircraft are safe and that pilots get the training they need," the Texas Republican added.