If they are all BA or finnair or any of these large legacy multi fleet companys you won't get me accepting a conditional clearance unless it something sensible like after the 747. But if its in the realms of picking a 2 engined 737 sized aircraft out from similar sized aircraft that are all the same company its just not worth the risk.
Its that A320 737-800 size of aircraft its an issue with.
It was quite good when BA painted the tails with mankie colours it helped recognition no end.