In the event of a rapid descent with a large change in pressure, you might feel a short moment with the sound of the vario, weaker than usual, while using AIR³ 7.3 or 7.3+. This is due to a significant pressure difference between the inside of the unit and the outside. The pressure will quickly equalize and the sound will return to normal, but sometimes this can take precious seconds. To avoid such a situation, you can open the USB-C cover in advance, so that the inside is not sealed and the pressure equalizes instantly.