Aviation investigators are scratching their heads over a 10-person plane that took off with 2 pilots, but returned with just one ... after one of them fell to his death while they were midair.
An emergency landing went down at Raleigh Durham International Airport after 23-year-old co-pilot Charles Hew Crooks either fell or jumped to his death Friday while they were in the skies, according to federal authorities.
They were trying to get back to the ground as safe as possible after the plane lost its right wheel ... when Crooks exited the small 10-seater.
His body was found roughly 30 miles away, stuck in the trees of someone's backyard -- he had no parachute on him and authorities believe he fell 3,500 feet.
Both the Federal Aviation Authority and the National Transportation Safety Board are investigating whether or not he died before the fall.
The other pilot was taken to a nearby hospital with minor injuries, and released the same day.
Crooks' father, Hew Crooks, toldWRAL he's unable to process the news ... saying his son "wouldn’t trade places with anybody in the world. He loved where he was.”
Crooks, who was a flight instructor, got his private pilot license while just a sophomore in college ... and his father can't imagine what happened.