I am scheduled to fly JFK-LHR-ZAG. JFK to LHR is on AA. LHR to ZAG is on BA. The ticket was purchased through AA and includes both flights. I have purchased a Main Cabin ticket from AA which includes one free checked bag, free seat selection, and a free change. The layover at LHR is 2 hours and 20 minutes.

1. Am I correct that for a 2 hour and 20 minute layover, on a single ticket, with partner airlines (AA and BA), my bag will be checked through onto the ZAG flight and that I will not need to retrieve the checked bag at LHR?

2. If something goes wrong, if the flight from LHR to ZAG is canceled, or if the transatlantic leg is delayed and I miss the connection, will I then be asked to retrieve my checked bag?

3. If I have been asked to retrieve my checked bag, and I then recheck in at the BA counter for the rescheduled LHR to ZAG leg, will I now have to pay to BA a checked bag fee, or should BA honor the terms of the original ticket providing for a free checked bag?

4. I have heard all the horror stories about connections at Heathrow. Should I have any other contingency plans?

Thank you.