DETROIT — Remains of an Army pilot and an observer killed more than 50 years ago when their plane went down in Southeast Asia during the Vietnam War will be buried with military honors at Arlington National Cemetery in Virginia.

The Defense Department’s POW/MIA Accounting Agency says ceremonies for Staff Sgt. Marshall Kipina of Calumet, Michigan, and Lt. Col. Robert Nopp of Salem, Oregon, are scheduled Thursday.

Nopp, the pilot, was 31 and Kipina was 21 when their aircraft failed to return in 1966 from surveillance mission over Laos, which shares a border with Vietnam. Nopp piloted the plane.

On July 13, 1966 Kipina and Nopp were on a night surveillance mission from Phu Bai Airfield over Attapu Province, Laos, aboard an OV-1C aircraft, according to Defense Department records.

In heavy thunderstorms, visibility was poor as the aircraft flew its mission over mountainous terrain. Radar and radio contact with the aircraft were lost, and it failed to return as scheduled. Search efforts found no sign of it.

The crash site was identified in the 1990s and later excavated. The remains of Nopp and Kipina were accounted for earlier this year.