Not on AA.com, but reported by Air Canada and BMI (and probably others) from this thread on the BA board. Probably due to operational issues with dealing with the extra baggage and cancellations, UK airports are no longer handling baggage for connecting passengers (all baggage from a flight goes to the carousel) and carriers can't check luggage through (this I don't understand, as it's going to make queues longer with all those new people getting tags printed). As a result, Air Canada is asking 4 hours minimum connection time(!)

Obviously, if you're planning to connect through the UK, don't. I have acquaintances that were scheduked to fly through LHR, but lucklily was able to move them to connect at a secondary European airport.