EF Voice, thanks for looking at this!
That would make sense as it's an AA fare that you would have to fly on AA marketed flights in the Americas (IATA Area 1).
I was looking at other carriers' service for portions of the journey within Area 1 because I thought that was permitted under fare rules. Here are some relevant sections:
Code:
STOPOVERS UNLIMITED FREE STOPOVERS PERMITTED ON THE PRICING
UNIT.
TRANSFERS UNLIMITED TRANSFERS PERMITTED ON THE PRICING UNIT.
FARE BREAK SURFACE SECTORS NOT PERMITTED AND EMBEDDED
SURFACE SECTORS PERMITTED ON THE FARE COMPONENT.
FLIGHT APPLICATION THE FARE COMPONENT MUST NOT BE ON
ONE OR MORE OF THE FOLLOWING
ANY AF FLIGHT
ANY LH FLIGHT
ANY KL FLIGHT.
AND
THE FARE COMPONENT MUST NOT BE ON
ONE OR MORE OF THE FOLLOWING
IB FLIGHTS 5000 THROUGH 5999
IB FLIGHTS 7704 THROUGH 7705.
AND
THE FARE COMPONENT MUST INCLUDE TRAVEL VIA EACH
TRANSATLANTIC SECTOR BUT NOT ON
ONE OR MORE OF THE FOLLOWING
AA FLIGHTS 5100 THROUGH 8399.
Notice: Few carriers are excluded. For example, fine to take LA within south america. But with unlimited transfers and unlimited stopovers, subject of course to the MPM, one can imagine zig-zagging around the US a bit. CDG-JFK-ORD-MIA-EZE-SCL or what have you. But under the rules I quoted above, you might think the routing coculd just as easily be CDG-AA-JFK-DL-MSP-... Do you see any fare rule excluding this? As I said, it's a great and flexible fare!
Why would AA let you fly another carrier to/from BOS and DFW, cities that AA itself serves?
First, the TPD text I quoted seemed to offer a deduction "VIA DFW AND/OR BOS". Note "OR". Travel via just one of those cities would suffice. No obligation to travel via both DFW and BOS to get the deduction.
Why would AA let pax fly other carriers? It's a flexible fare, allowing unlimited stopovers and transfers, so I guess AA thinks those benefits help attract passengers with specific requirements. You can imagine a passenger whose routing needs or schedule needs are best served with some segments on other carriers, but of course with the transatlantic segments on AA as they must be.
The IATA area restrictions are also listed in the Fare Rules, you should read that as well.
I read the entire text captioned "Fare Rules Results" in ExpertFlyer. I did not find the restriction "PROVIDED ALL TRAVEL IS ON AA WITHIN AREA 1" that AA claims is in the fare rules or routing rules. Do you see that there? Where can I get that?
If you (or others) would like to look at this DFR fare in order to see what I'm seeing, note that it's a historic fare -- so enter a past ticketing date. I enter CDG to SCL, outbound 4/5/14, return 4/12/14, ticketing date 4/4/13. Then DFR does appear in the list of fares in the market.