At 04:48 central time, a Cessna 421B struck terrain while maneuvering near Norman, killing the pilot and his passenger. The flight originated from Altus, Okla., and was destined for Norman. The airplane was VFR over-the-top and requested an IFR clearance to the Westheimer Airport. The pilot was cleared for the localizer runway 03 instrument approach. Subsequently, ATC approved the flight to change to the airport advisory frequency, the pilot acknowledged, and no further communications were heard from the flight. A police officer who was patrolling the airport heard an airplane overfly runway 03 but did not see the airplane or any lights. The airplane was located one mile northeast of the airport on a heading that implied he had begun the missed approach turn.