Dennis Sellers on the wonderful AirFly Pro:
The wireless transmitter plugs into those jacks normally reserved for wired headsets and transmits the sound to your wireless headphones. It has a built-in battery that lasts up to 16 hours, after which time it can be recharged via USB-C.
Great for long flights but works on a TV or car, too. All it needs is a standard headphone jack; then just sync up AirPods or wireless Bluetooth earbuds.