With a handful of major and minor airports, the two cell carriers tiny portfolio will have bilateral roaming: This tiny deal represents airports as large as Denver and properties like Salt Lake City that aren't up and running yet, and shows the incremental and tedious steps taken to stitch together networks. The significant fact is that the two networks, which currently mostly resell Wayport locations, are willing to work directly together with bilateral roaming.
It's part of a strategy: neither company could possibly have more than a few hundred monthly unlimited customers because it's cheaper to pay Wayport or Boingo Wireless for unlimited access to the subset of locations and then pay as you go on occasion in certain airports. AT&T Wireless charges the absurd price of $70 per month.
Sprint PCS, however, is starting their build-out in a big way, and AT&T Wireless resells Cometa locations (though it doesn't list them in its Wi-Fi directory), which aren't yet part of Wayport's networks.