The 100th Air Refueling Wing flew a KC-135 Stratotanker to Romania to conduct air refueling training with the Romanian.
Supersonic Flight, Sonic Booms Explained
When an aircraft passes through the air it creates a series of pressure waves in front of it and behind it, similar to the bow and stern waves created by a boat. These waves travel at the speed of sound, and as the speed of the object increases, the waves are forced together, or compressed, because they cannot get out of the way of each other. Eventually they merge into a single shock wave, which travels at the speed of sound, a critical speed known as Mach 1, and is approximately 1,225 km/h (761 mph) at sea level and 20 °C (68 °F).