I have never flown BA out of SEA, but if they can't source superb fish there, then there's no hope for the meal at all.

Having said that, I would agree with others that you're unlikely to find food on a plane that is better than that of a good everyday local restaurant (in my case that would be The Ivy ). It certainly isn't haute cuisine, although sometimes they will use some expensive ingredients, or you'll get something local that you haven't had before.

On the other hand, the wines should be superb compared to those you're likely to drink in a restaurant, unless you normally delve into the expensive lower reaches of a good wine list. I would focus on enjoying those.

All in all, the only places I can think of that serve a more extreme combination of better wine and worse food are the High Tables of the older Oxford and Cambridge colleges and perhaps certain St James's clubs (although the best beef I have ever had by a large margin - far better than Wagyu beef, at least in London, - was surprisingly in White's).