From memory, when APD was raised around 2006/7 Ryanair chose to insist passengers pay the extra while BA just swallowed the loss on the behalf of customers. I think one of the reasons is that BA gets a lot of corporate traffic and invoicing and collection would be deemed problematic - especially requiring travel management companies to invoice their clients who would then charge corporatd cost codes requiring companies to chanfe annual budgets and causing huge amounts of trouble in company finance and accounts departments. Because Ryanair tends to sell predominantly direct and had minimal involvement with corporate purchasing in companies they didn't need to care.
So what was Virgin / Easyjet / Flybe and every other airlines excuse then as they imposed the APD?
Reality is invoicing and collection is easy as just rebill.
It was reckoned that it cost BA £11 Million and the idea that customers are grateful afraid doesn't stand up to research.
Majority of actual passengers flying on corporate business would have no idea of the fare paid as its booked for them and given the add on that the agencies have it makes little difference. Next time rebooking they wouldn't think I saved £100 with BA last time..
There was research done in 90's about beer price increases that when someone read beer going up by 5p a pint they pissed off (pardon the pun) and claimed would go to a pub that didn't put prices up or would reduce consumption.
Reality was study showed that within 2 weeks the customer was back and drinking same amount and within 4 weeks didn't remember price had been increased.