Let's "unspin" your Spin a bit. The total International O&D (YE 9/2007) for US based carriers at IAD was 2,878,400. The total for PHL was 2,898,018. Since US and UA are essentially the only US based carriers flying internationally from these airports, these numbers closely, if not exactly, represent their actual O&D passenger counts. A further advantage at PHL for US, versus UA at IAD is that 20% of all international flights are on international carriers, whereas that number at IAD is 51% - much more competition. San Juan is not considered International in these numbers. Further, PHL has a almost Twice the Domestic O&D of IAD. I will admit that IAD Possibly has better "quality" (more premium passengers) international O&D than does PHL, but I'd speculate that is principally driven by US's service quality; otherwise, it's unlikely BA/AF would be as successful at PHL as they are.
Nice try but
your "spin" leaves a lot to be desired.
First, your numbers are not O&D but are, in fact, enplanements/deplanements. Big difference. O&D includes only those passengers starting or ending their trip at an airport (IAD and PHL in this case), while enplanement/deplanement numbers include the true O&D passengers as well as those passengers making a connection at the hub. Your so-called "O&D" numbers aren't even close to the real ones.
Second, I do have access to the DOT-restricted international O&D database and can tell you that IAD's total international O&D passengers are 20% higher than PHL's, IAD's average fare for all international O&D passengers is 79% higher than PHL's, and IAD's total international O&D revenue is a whopping 115% higher than PHL's (sorry but the actual numbers behind the percentages are not allowed to be shown on a public forum like this one). And only U.S. carriers file their international O&D data with the DOT with virtually no public distribution (
i.e., it's not on the BTS website).
Third, the international O&D at IAD and PHL doesn't include only UA's and US' data on nonstop flights but also
ALL U.S. carrier data for passengers traveling via other domestic hubs as well. For example, IAD-CCS and PHL-CCS passengers carried by AA over its MIA hub are included in each airport's respective international O&D totals despite not being flown nonstop.
Fourth, your comment about competition by foreign carriers overlooks the fact that many of those 20 -- soon to be 21 -- carriers at IAD (such as AC, LH, NH, OS, SA, SK and TA) codeshare with UA, significantly improving the carrier's international offerings at its IAD hub, while only one (LH) of the five foreign carriers at PHL does so with US. Moreover, the presence of numerous foreign carriers at IAD is also indicative of the strength of the international travel market in the Washington area and, despite the added competition, that's a good thing.
For some additional data, read my post in the thread that
whlinder linked to above. And to reiterate my conclusion from that post,
The fact of the matter is that IAD has far more international passengers than does PHL, on both an enplaned/deplaned basis and an O&D basis. ... So IMHO, anyone who thinks that PHL would be the premier east coast international gateway [rather than IAD] for a merged UA/US, especially if United is the purchaser, will likely be sorely disappointed. The data simply doesn't support any other conclusion.
Thanks for all the info though. Much appreciated. We are all just going to have to go with the flow if this merger happens. 
