Originally Posted by GuyFromBOM

Avoid LHR, if you plan to connect onwards onto an AI flight.

AI is still at LHR T4, while all other *A carriers are at T2. The delay has something to do with the contract of their lounge at T4, which is due to expire later this year. Following which they should move to T2.

The AI Lounge at T4 is pre-security. Nothing fancy, but functional. Isn't operational 24x7, but opens up a few hours before STD.

On a side note, have you considered the flying F on LH via FRA. The LH F lounge is awesome i hear.