Hiya
I think in the UK its 3 different types of a/c, so probably 737, 757, 319 or something like that at BA? I'm not sure what happens if there's more than 1 type of that a/c though eg 737-500 and 737-800 say. I know when I used to fly the 757 + 767-200 + 767-300 the 767s were classed as 2 different a/c!!