What happened to a Philadelphia-born Army captain who disappeared in Vietnam in 1969 is a mystery no more.

The remains of Charles R. Barnes have been identified, the Department of Defense Prisoner of War/Missing Personnel Office (DPMO) announced Monday.

He will be buried with full military honors Wednesday at Arlington National Cemetery.

On March 16, 1969, Barnes and four other service members were flying toward Da Nang and Phu Bai when communications contact with their aircraft was lost. Hazardous weather made a thorough search difficult after their plane failed to land. All five were listed as missing in action, and Barnes is the last whose remains have been accounted for, said DPMO spokeswoman Jessica Pierno.

Barnes, nicknamed "Sonny," was raised in Fullerton, Lehigh County, and graduated from Whitehall High School in 1960, according to an obituary in the Allentown Morning Call. He is survived by a son, Charles; a grandson; and a sister.

Pieces of the puzzle have taken decades to put together.

Remains turned over by Vietnam in the late 1980s could not be identified at the time.

In 1993, a joint U.S.-Vietnamese investigative team located a Vietnamese citizen "who supplied remains and an identification tag bearing Barnes' name, which he claimed to have recovered from an aircraft crash site," according to Monday's announcement. In 1999, more interviews led investigators to the crash site, where remains and other evidence were recovered in 2000.

Scientists "used circumstantial evidence, and forensic identification tools such as mitochondrial DNA — which matched that of Barnes' sister — in the identification of the remains," the Defense Department said.

Contact staff writer Peter Mucha at 215-854-4342 or pmucha@phillynews.com.