I apologize if this has been asked/answered but I didn't see it on here and can't seem to find anything via google.

My husband and I both have BA chase cards and have for years. (We are Americans if that matters.) We both earned the companion/travel together ticket on each of our BA cards in 2020, 2021, and 2022. (I already have used/booked or planned to book a trip with all of the aforementioned passes and now trying to save up avios and companion tickets for a summer 2024 trip.) I have nearly met my 30k minimum on my BA Chase card to earn my travel together/companion pass onBA my card this year. However, my husband has spent almost nothing on his BA card this year. Since his BA card is several years old and he would now qualify for a new SUB (i.e. sign up bonus) if he closed it out and reapplied for the BA card, I was considering having him doing that so that he could both get the companion/travel together while also getting the 100k or so bonus miles.

However, then I saw where Aer Lingus (which we don't have a card for) has the same bonus offering that BA has and also offers the travel together ticket. I was thinking of, perhaps, instead of having him close down that BA card just having him apply for the Aer Lingus instead and leaving the BA card open. However, I wasn't sure if he could transfer that companion pass to BA in the same way you can transfer Avios. Can he? Or, alternatively, is it relatively easy to book a BA flight with Aer Lingus? I know they are both in the One World Alliance. I prefer to fly out of IAH.