There’s a press release on the relevant Carnival Corp. webpage that announces that for Adonia’s 2017/18 Caribbean season – that is, next winter – P&O have contracted with Virgin Atlantic to provide the flights from Manchester and Heathrow to Barbados, and some seats in existing (public) flights from Gatwick. Here’s a link to the relevant page.
I gather that using a carrier other than Thomas Cook or Thomson for these Caribbean cruise flights is quite unusual. It’s not clear what the reason is for the decision – it could be that Virgin Atlantic came in with a great bid, or perhaps the regular airlines had no capacity available. Following her announced release from Fathom, Adonia’s Caribbean programme has been arranged at short notice and later than that for other ships.
While Virgin Atlantic gets a general thumbs-up, one person who commented on this pointed out that on a flight (non-cruise, I believe) to Barbados with Virgin Atlantic a few years ago, the aircraft used was older and not comparable with Virgin Atlantic services to Miami and New York. We’ll know more by this time next year!