Irregular Operations
Irregular operations come part and parcel with air travel. Expect the best but prepare for the worst. In other words, allow plenty of wriggle room in your travel plans, think twice about short connections at MIA during the hurricane season, or at JFK in winter, or at ORD at any time other than spring and fall, noting Chicago's spring and fall seasons while lasting no more than a week each Mother Nature is inclined to blast Chicagoland with her wrath during these short seasons.

Although AA tend to be very helpful rearranging flights, they do often work on the basis of getting you onto the next available service irrespective of fare class. So, for example, If you face a weather related delay they are particularly unwilling to more than that. However if you look at Expert Flyer before approaching the Admirals Club agent then you can be proactive in making suggestions. Note, in rebooking AA flights, there is a risk of instant upgrades ending up as business or worse, economy. If the next available flight is sold out in first, AA are often open to requests for a seat on the following flight that has seats available in first class. This may involve joining the stand-by list. Working with Gate Agents or AAdmirals Club staff pays dividends. It pays to check revised booking class(es) with the agent. This is your only opportunity to ensure the flights are rebooked into the same class as your original booking (A and/or P), and your Tier Points post as planned.

Original Routing Credit
ORC allows you to claim credit for your original routing as you originally booked it in the event you are rerouted on flights that earn fewer Tier Points than you originally booked.

If you booked with BA on a 125 ticket it's in the T&Cs, and there will be no push back should you need to submit a ORC claim, though you will have to claim manually and it will take a few weeks to clear. Occasionally, if the irrop was at the very last moment you'll get the ORC anyway and automatically.

The only stickiness relates to 001 ticket and rerouted on another oneworld flight (typically a re-routed and/or downgraded AA service) which gets less TPs and Avios. In that scenario if you claim ORC, BAEC pushes it to AA (since they are the ones who "pay" the Avios) and their view can be that you get what you travelled and a refund for anything you didn't travel.

Remember that whatever happens to keep your boarding passes, a note of the new PNR, the BA PNR, and the BA ticket number. And don't forget to claim your miles credit for the service if you end up travelling on another alliance, giving the number at the gate or check in, that form of double-dipping has long been considered acceptable.