In every war, "boys" go to war as young men. Despite being young men, their youth and being a mother's son still makes them "boys". The populace of countries even refer to soldiers as "our boys".
When a flyer is shot down, in honor, pilots fly a "Missing Man" formation. Since all US Military divisions--Army, Navy, Air Force--have wing divisions, any Military rite or observance could fly the Missing Man formation as a remembrance.
"Planes up in the sky" - a military formation
"There's a missing man" - a soldier who died, shown by a missing plane in the formation
"A boy who didn't make it" - a mother's son who perished