That’s the capability to connect AirPods Max to analog sources such as the inflight entertainment on an airplane which, almost universally, still requires a cable link to a 3.5m

Apple has said its AirPods Max wireless headphones will soon support high-fidelity lossless audio. Available through a software update in April, the new feature will allow users to listen to 24-bit, 48kHz lossless audio on the AirPods Max. However, the caveat is that lossless audio will work only with a cable on the latest AirPods Max model.

The upcoming update will make AirPods Max "the only headphones that enable musicians to both create and mix in Personalised Spatial Audio with head tracking."