The deadly mid-air collision involving two U.S. Army helicopters in Alaska last week happened with no weather issues or visibility problems, a report says. 

John Pennell, a spokesperson for the U.S. Army Alaska, told The Associated Press that conditions were calm Thursday when the two AH-64 Apache helicopters struck each other over a rugged and mountainous area near Healy, leaving three soldiers dead and a fourth injured. 

Investigators are planning to fly Monday morning to the accident scene 50 miles east of the small town, he added, noting that the surviving soldier, as of Sunday, remains hospitalized. 

Fox News Digital has reached out to Pennell for further comment. 

ARMY RELEASES IDENTITIES OF SOLDIERS KILLED IN ALASKA HELICOPTER CRASH 

AH-64D Apache Longbow attack helicopters

The deadly collision involved two U.S. Army helicopters and left three dead. (Cameron Roxberry/U.S. Army via AP)

The cause of the crash near Fairbanks remains unknown. The helicopters were returning to Fort Wainwright after a training mission when they collided. 

The deceased have been identified as Chief Warrant Officer 3 Christopher Robert Eramo, 39, of Oneonta, New York, Chief Warrant Officer 2 Kyle McKenna, 28, of Colorado Springs, Colorado, and Warrant Officer 1 Stewart Duane Wayment, 32, of North Logan, Utah. 

"The battalion is devastated and mourning the loss of three of our best," said Lt. Col. Matthew C. Carlsen, the 1-25th AB commander. "Our loss, however, cannot be compared to the suffering and loss which the family members of Chief Warrant Officer 3 Chris Eramo, Chief Warrant Officer 2 Kyle McKenna and Warrant Officer 1 Stewart ‘Stew’ Wayment are experiencing." 

ARMY SENDS INVESTIGATORS AFTER FATAL ALASKA HELICOPTER CRASH 

A sign at the main entry point to U.S. Army Garrison Alaska Fort Wainwright

The helicopters involved in the crash were heading to U.S. Army Garrison Alaska Fort Wainwright in Fairbanks, Alaska. (Eve Baker/Fort Wainwright Public Affairs Office)

"The entire team has come together to focus our thoughts, prayers, and actions to provide and sustain them with whatever comfort and support they need at this time, and I promise that this will continue long into the future," Carlsen added. "Our mission now is to focus on the families, the survivors and to honor and cherish their memories. Chris, Kyle, and Stew will forever be ‘Little Bears,’ ‘Vikings’ and ‘ToughOnes’ of the Arctic Attack." 

In the wake of the crash and a Black Hawk helicopter accident in Kentucky that killed nine in March, the Army has grounded its aviation units for training. 

The suspension of air operations was effective immediately, with units grounded until they complete the training, said Lt. Col. Terence Kelley, an Army spokesperson. For active-duty units, the training is to take place between May 1 and 5. Army National Guard and Reserve units will have until May 31 to complete the training. 

Fort Campbell Kentucky military helicopter crash

The U.S. Army is conducting aviation training starting today in the wake of the Alaska crash last week and one involving two Black Hawk helicopters in Kentucky that killed nine in March. Investigators are shown here arriving at the scene of a crash in Trigg County, Kentucky, on Wednesday, March 29. (WZTV)

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"The move grounds all Army aviators, except those participating in critical missions, until they complete the required training," the Army said in a statement. 

"The safety of our aviators is our top priority, and this stand down is an important step to make certain we are doing everything possible to prevent accidents and protect our personnel," added Army Chief of Staff James McConville. 

Fox News’ Adam Sabes, Julia Musto and the Associated Press contributed to this report.