Are you talking about "check in" or "arrival tinme at LHR?

If you're not checking bags, why not just check-in the night before w/ on-line check-in at aa.com, print your boarding passes, and go straight upstairs to the Fast Track lane?

(Just did that last week, for that flight, arriving at LHR at 6:30am, with plenty of time to grab a quick shower & enjoy breakfast in BA's lounge pre-flight).