It depends...if they're both for the same academy, of course accept just one. If they're for different academies, accept the one to the academy you want to go to more. Another angle: If you have an LOA for one and it's your first choice, accept it only for that. If you have an LOA for a second choice and not a first, think hard and if you think you can be accepted into your first choice, go for it, but accept both noms for a backup. Finally, if you have no LOAs, accept both as a safety net. That's what I'd do.