Originally Posted by
best
Thank you: while interested in general about this question, here is specific example: SNA-ORD-MIA. Depart at ORD, and reboard same plan about one hour later. One AA flight number. Posted only 2,331 miles.
From aa.com:
Q: How are miles calculated if my trip includes a through flight?
A: A through flight occurs when your flight stops to pickup or drop off passengers, and you continue to your destination on the same or a different aircraft with the same flight number. Our system is set to calculate mileage credit based on flight numbers, and does not recognize that there was an enroute landing associated with your flight. Therefore, if your itinerary includes a through flight, the miles you earn will be calculated as a nonstop segment.