I'm sure there is more to this story. Circa 1999, Corpus Christi lost an instructor whose seatbelt had been unlatched during the control check. The buckle was susceptible to this and there were numerous Read and Initials (FCIFs) covering this problem.
While unaware of his unlatched seatbelt, the doomed IP watched/instructed as the student departed the field, entered the working area, did checklists and clearing turns and prepared for the first maneuver...spin recovery. T-34 spin recovery was full opposite rudder, stick slightly forward of neutral. This student put the stick to the forward stop and as the aircraft exited the spin, the negative Gs literally launched the IP through the plexiglass canopy.
He opened his parachute appropriately, but unfortunately, then released the buckles too early and ended up falling an estimated 300 feet to the water. They believe that he thought he was much lower and was doing the procedure properly.
Anyway back to this mishap. You never know when something unexpected will happen and your seatbelt will make all the difference. Wear it, check it and double check it. It is not the routine things that kill you, it is the surprise things that take you down.