Mumford was last seen in Portland, Oregon on July 7, 2007. A retired commercial airline pilot, he had recently purchased a bright yellow single-engine 2007 Cub Crafters Sports Cub aircraft with the tail number N222TB, and was making local familiarization flights. He flew out of Aurora Airport shortly after 5:00 a.m. on July 7 and never returned. His family reported him missing that night.

A photograph of a plane similar to Mumford's is posted below this case summary. If it had a full tank of fuel, it could have flown as far as 400 miles without needing to stop. Neither the plane's emergency responder nor Mumford's cellular phone are emiting any signals. Mumford is a very experienced pilot; he worked for TWA and American Airlines for over 35 years and had an estimated 27,000 hours of flight experience. He was in excellent health at the time of his disappearance and participated in triathlons. An extensive search turned up no sign of him or his plane. His case remains unsolved.

Above: Plane similar to Mumford's