Originally Posted by
FWAAA
Different sources will give slightly different numbers, but I agree with
elitetraveler that PHL is a fortress for US+AA.
For the 12 months ended 5/31/14, WN, UA and DL had ~18% of the domestic share according to the BTS:
http://www.transtats.bts.gov/airports.asp?pn=1
UA and DL had small amounts of regional capacity into PHL as well, but nearly all the regional flights belonged to US.
Those numbers measure just domestic market share. US+AA(BA) has practically all the international market share at PHL, so 79% appears to be reasonable data.
You seem to have ignored the OTHER 30% in the DOT list - which should be the only determination of achieving the 70% definition of Fortress Hub and the source for my earlier claim.
I'd actually prefer that PHL NOT achieve Fortress Hub status as it reduces the interest of foreign carriers in starting service. Look at what has/is happening at BOS as an example. It could, of course, be speculated that OW will result in more international carriers serving the region due to the vast US/AA domestic feed at PHL, but that remains to be seen.