I’ve had challenges too but generally after trying to connect a few time it has managed to work. Here are the steps I used:

1. turn on the IFE bluetooth
2. AirPods should be in the case and disconnected from phone
3. Open lid to AirPod case.
4. Press button on back of case and hold until flashing white LED appears.
5. Select your device on IFE screen.

It sometimes takes a few tries and the difference is usually disconnecting the phone first.