Pairing Apple AirPods with 3.5mm Aux Audio Bluetooth Transmitter Adapter.

The Bluetooth adapter is a Mpow (MPBH045AB) which can work as both transmitter and receiver.

Full written review on Amazon UK here:
https://www.amazon.co.uk/gp/customer-reviews/R3J5L0OERAC2HC/refcm_cr_dp_d_rvw_ttl?ieUTF8&ASINB01KZR6S6W

Summary steps:
1) check that the Mpow mode switch is set to Tx (transmitter mode)
2) Press and hold the power button on the Mpow adapter until it turns on – it will immediately enter pairing mode with the green LED flashing (it flashes blue in receiver mode)
3) Open the AirPods case – the internal LED light will display green/yellow depending on the charge level. Press and hold the button on the AirPods case for about 3 seconds to start pairing mode – the internal LED will flash white.
4) After a few seconds, the Mpow green LED will turn solid green. The internal light on the AirPods case will also turn solid green. This indicates successful pairing.
(Sorry that the exposure in the video clip does not accurately display the colors of the LEDs)
The 3.5mm audio cable can be connected before or after pairing. It does not matter.

I also tested pairing the Mpow adapter in Tx mode with a pair of Anker Bluetooth Surge audio headphones and my wife's Bose QC35 headphones. The process was equally simple and successful.

Disclaimer:
I'm not a regular reviewer of anything, nor is this a sponsored promotion disguised as a review. Hence the relatively poor video quality. I decided to post this because I couldn't find anything online that clearly shows that AirPods can be easily paired with a Bluetooth transmitter.