ELMENDORF AIR FORCE BASE, Alaska — Four airmen were killed in a cargo plane that crashed during a training run at an Air Force base, military authorities said today. The crash sent a fireball hundreds of feet into the air, witnesses said.

Three of the men were in the Alaska Air National Guard and the fourth was on active duty at Elmendorf Air Force Base, Air Force Col. John McMullen said. Their names have not been released pending notification of relatives.

The C-17 was from the 3rd Wing, based at Elmendorf near downtown Anchorage. The crash happened about 6:14 p.m. Wednesday during a training demonstration for an upcoming weekend air show, Lt. Gen. Dana Atkins said.

The crash is the second in Anchorage this summer. In June, one child was killed and four others burned when a small plane crashed after taking off from the city's small-airplane airport downtown.