They've successfully grown the market as we can see, the first winter season in a UK regional transatlantic route would likely be a loss maker, surely that has been factored in?
Oddly enough American's presence also reminds people that United offer a direct routing as well, so oddly enough it can be a win for the airport if both carriers can find a mature niche. UA have not managed to grow the market beyond that one daily whereas at EDI they're up rto three daily in summer so good to see someone else trying to crack it.
Of course we're not far from having to replace those B757s and that's an issue for all UK regionals that can't support a year round B788. Where's there's a will there's a way though