NASA said that ‘Cavum clouds’ form when aeroplanes pass through layers of altocumulus clouds, which are mid-level clouds containing supercooled water droplets . As the aircraft moves through, a process known as adiabatic expansion can cause the water drops to freeze into ice crystals, creating a hole in the clouds . In the picture, the National Aeronautics and Space Administration (NASA) shared a photograph showing what are seen as ‘odd holes’ in