Originally Posted by
rucksack
Not really. Delta owns a large share of Aeromexico and they operate a JCA. Both airlines market flights where one is the operating carrier for one leg and the other is the operating carrier for the other leg. Who would be the "third party" in this case?
If you booked a Delta flight through American Airlines (yes, this is possible, thanks to their reinstated interline agreement), I suppose it would be fair to say that American Airlines is the travel agent. But I don't think that logic applies to codeshare partners.
Anytime an airline books a flight marketed by another airline, they're doing so as a "travel agent." Last time I checked that exact wording was even in the contract of carriage. They may contractually be able to do more for close partners, but nonetheless it's still viewed as acting as a travel agent for the OAL.
For this purpose, codeshare flights are considered flights of the marketing airline. Thus a DL codeshare on AM metal is actually considered a DL flight. If DL booked an AM codeshare on DL metal, even though in the end passenger will fly DL, they're acting as a TA for AM in selling the AM marketed flight.