The victims were not immediately identified, pending notification of relatives. Their remains were removed from the scene Tuesday as members of their unit took time to grieve the loss.
The two-seat OH-58 Kiowa Warrior observation helicopters crashed after 8 p.m., according to officials.
It was not immediately clear whether the aircraft collided or crashed separately. The cause remains under investigation.
Chief Warrant Officer 5 James Oliphant, an aviation safety officer at the base, said the aviators' colleagues have halted further activity as they analyze and grieve the tragedy.
"Right now the organization will stand down to begin the healing process," Oliphant said.
The single-engine, four-bladed aircraft are used for armed reconnaissance.
Oliphant said the airmen were on a routine night training flight, but he did not know specifically what they were doing before the crash.
According to Oliphant, the investigation could take several months or up to a year.
The Associated Press contributed to this story.