On 23 March 1992, near
Amarillo, Texas, Steven Douglass photographed the "donuts on a rope"
contrail and linked this sighting to distinctive sounds. He described the engine noise as: "strange, loud pulsating roar... unique... a deep pulsating rumble that vibrated the house and made the windows shake... similar to rocket engine noise, but deeper, with evenly timed pulses." In addition to providing the first photographs of the distinctive contrail previously reported by many, the significance of this sighting was enhanced by Douglass' reports of intercepts of radio transmissions: "Air-to-air communications...
