The NTSB considered the possibility that the explosive residue was due to contamination from the aircraft's use in 1991 transporting troops during the Gulf War or its use in a dog-training explosive detection exercise about one month before the accident.
The NTSB considered possible reasons why the wreckage would test positive for explosive residue, including the aircraft’s use in 1991 transporting troops during the Gulf War, as well as its use in a dog-training explosive detection exercise about one month before the crash.