There are actually loads of permutations....here are some random thoughts in no particular order...
- AL flies 330/350 wide bodies on lhr route at peak times only releasing slots for BA longhaul
- AL feeds into LHR and services UK regions for BA just as it has for Little Red. BA then turns a profit on regional due to the significantly low cost base which AL has
- AL takes over Lgw routes utilising it's lower cost base and again makes loads of profit
- Some BA or AL flagged aircraft fly lhr/dub then onto US utilising CBP facilities
- big cull of back office staff/middle management at AL as no longer needed once integrated into BA which in turn generates huge underlying profitability