Using the schlieren photography technique, NASA was able to capture the first air-to-air images of the interaction of shockwaves from two supersonic aircraft flying in formation. These two U.S. Air Force Test Pilot School T-38 aircraft are flying in formation, approximately 30 feet apart, at supersonic speeds, or faster than the speed of sound, producing shockwaves that are typically heard on the ground as a sonic boom. The image, originally monochromatic and shown here as a colorized composite image, was captured during a supersonic flight series flown, in part, to better understand how shocks interact with aircraft plumes, as well as with each other.
For more information: https://www.nasa.gov/centers/armstrong/features/supersonic-shockwave-interaction.html
February 2019
NASA Photo