My 12/20 LHR-MIA flight was cancelled, and I was rebooked on 12/24. I & my niece took the 5:44am underground to LHR. AA terminal 3 was a ZOO. First class check-in (G?) was closed.

We got on the waitlist for #87 LHR-ORD 10:15am. We waited, waited, waited by ticketing area. At 9:40am I heard an AA rep say she had 10 seats on LHR-DFW 9:55am. Whoever was there got them. I said yes, but while we were waiting for our boarding passes, we both cleared on AA 87. I thought we would be in the back of the bus, but I got F (J revenue ticket with eVIP) & my niece got J seat (on coach with eVIP upgrade). Pretty slick, huh? However, the flight boarded 1-hour late then we sat on the plane for 3 hours. But got out finally. I was soooo over that cold London weather.

So, the lesson? It pays to be proactive, and keep your ears open.
I was generally surprised how LHR ground to a halt with moderate snow. The AA staff were very nice but seemed overwhelmed. It took ages to issue a simple boarding pass or luggage tag. AA agents in US seem much quicker & efficient, but perhaps it is computer system at LHR. Just glad to be in US, although delayed here due to snow (projected arrival in MIA 3am)