Transcript for Missing Marine laid to rest nearly 50 years after plane shot down in Vietnam War

On this memorial day weekend as we remember those who sacrificed we pay tribute to one service member, a marine missing in action for nearly 50 years and his family's journey to bring him home. ??? My dad Billy Ryan was an all-American Irish catholic boy from north Jerry. My dad lived his life of purpose. He always wanted to do something that was meaningful. When the Marines were there saying he could learn to fly planes and be part of making a difference and serving his country that resonated with him. Reporter: Michael Ryan didn't really know his dad has spent a lifetime learning about him. Michael was only 3 months old when his father first lieutenant Billy Ryan just 24 years old was sent to fight in Vietnam. It was 1968. Ryan was a radar intercept operator flying in the backseat of f-4 phantom fighter jets. He flew over 300 missions in nine months. Just days from his son's first birthday and planned r&r, Ryan had one more mission. They were actually bombing the ho chi Minh trail and hit by anti-aircraft missile and their plane was shot down and the pilot was able to eject. My father was not. Reporter: Lieutenant Ryan among the 2600 Americans missing in action. There was always that, you know, 1% chance that did he live? Did someone not see his parachute? Was he a powerhouse? As a young child I mean it was always a dream. I'd sleep and wake up to imagine if my father came home to me, you know. That was something I always kind of held out hope for and I think secretly my mom did too so I wanted to do something more for him and wanted to bring him home and found out Marine Corps was doing that all along. Reporter: In 198820 years after he disappeared. U.S. Excavation teams were finally allowed wide access in southeast Asia to search for the missing. I was learning they were finding pieces and parts of the aircraft, I was finding that they may have found a strap from the parachute however there wasn't anything substantial in terms of my dad's remains until recently. Reporter: Military teams took seven trips overseas spanning several years. Finally a positive I.D. First thing I did was call my mom. I mean she was -- I never heard her that excited and elated. Tears of joy and relieved, you know, I could feel that she had closure and to me that was the best feeling. Reporter: After a nearly 50-year journey, this month Mike Ryan finally bringing his dad home. First lieutenant William Ryan memorialized with full honors. But the moment bittersweet, an empty chair for Mike's mother, she knew her husband's remains had been found but passed away days before the service from cancer. I know in my heart, you know, she was there looking down because it was an amazing day and, you know, I just couldn't be more prouder of my father and his service to our country. My dad is buried at Arlington national cemetery and that's a special place to be. That's reserved for heroes and so this is going to be a special memorial day for myself as well as all my family and all the Ryans. And we honor the Ryan family service this memorial day weekend. That's all for us today. Thanks for sharing part of your Sunday with us. Check out "World news tonight" and have a great day.

This transcript has been automatically generated and may not be 100% accurate.