Both of the above.
Look again at
bisonrav's example above and remove the oneworld restriction. Anyone actually wanting to travel between PHL and DTW will find DL hard to beat: several nonstop flights with flight times starting at under 1:40. AA has a couple of nonstop flights, but they tend to be more expensive. Fly with AA via ORD or CLT, however, and you can match or beat DL's price. The downside (for people outside of this thread) is that it will take you between four hours (best-case, probably not at the lowest price) and seven hours in each direction. So on this route AA is most interesting to highly price-sensitive passengers -- or people hungry for tier points.
Thanks.. I figured as much. (may be new poster here but have done my homework here over the years
)
I'm well aware of the Delta (even Spirit) deals to DTW, I have friends there and try to go visit them as much as possible when the flights are worth it... the AA flights, that is
I took your example and stuck it in ITA, as I'm on the ongoing quest of learning about fare rules. It says 2 transfers are allowed, now, I'm playing with intermediate airports to find a combo similar to the PHL/CLT/RDU option.