The Sonic Boom Rescue - How the SR-71 Sent Secret Messages in the Vietnam War

In the afternoons of May 2nd and 4th of 1972, tri-sonic booms rang out over Hoa Lo, also known as the Hanoi Hilton - the largest Vietnamese Prison Camp of the Vietnam War. Two SR-71 Blackbirds had broken the sound barrier, carefully allowing 15 seconds to pass between each boom in order to send a secret message to the waiting prisoners of war. The sound was to serve as a signal and promise of freedom and were the result of a daring and courageous communications network established within the prison. A Navy Seal rescue mission was on the way... however, dissent in the prison would greatly complicate the operation, codenamed Thunderhead