On December 15, 1944, Maj. Alton Glenn Miller, commanding officer of the Army Air Force Band (Special), boarded a plane in England bound for France with Lt. Col. Norman Francis Baessell. Somewhere over the English Channel the plane vanished. No trace of the aircraft or its occupants has ever been found. To this day Miller, Baessell, and the pilot, John Robert Stuart Morgan, are classified as missing in action.

Weaving together cultural and military history, Glenn Miller Declassified tells the story of the musical legend Miller and his military career as commanding officer of the Army Air Force Band during World War II. After a brief assignment to the Army Specialist Corps, Miller was assigned to the Army Air Forces Training Command and soon thereafter to Supreme Headquarters, Allied Expeditionary Force, in the UK. Later that year Miller and his band were to be transferred to Paris to expand the Allied Expeditionary Forces Programme, but Miller never made it.

Miller's disappearance resulted in numerous conspiracy theories, especially since much of the information surrounding his military service had been classified, restricted, or, in some cases, lost. Dennis M. Spragg has gained unprecedented access to the Miller family archives as well as military and government documents to lay such theories to rest and to demonstrate the lasting legacy and importance of Miller's life, career, and service to his country.