The term 'BOOM (PLANE EFFECT)' can be summarized as the loud sound created by an aircraft when it breaks the sound barrier. This phenomenon is also known as a SONIC BOOM, which is the five-letter solution to the crossword puzzle. SONIC booms are created when an aircraft travels faster than the speed of sound, which is approximately 767 mph. The sound wave created by the aircraft is compressed into a single shock wave, resulting in a loud noise that can be heard from the ground.