Things to look for in what might be a good airport wireless experience are:
Dual band Wifi – there is typically less congestion and interference on the 5 GHz band.
802.11 N or AC: the N specification allows MIMO, which can thrive in a multipath RF environment.
External antennas: a casual airport guest will never see the wifi Access Point, however, external antennas can be utilized which have a higher receive signal sensitivity. A higher signal sensitivity can allow the wifi access point to work with low powered wifi devices.
Here are some wifi spectrum snapshots of various airports. Airports can upgrade their internet bandwidth at any time, so measured speeds can change.
Also, airports can add and remove wifi equipment at any time.
Tulsa airport Gate B5 by Southwest airlines, 2.4 GHz
St. Louis Lambert airport gate E10
Dallas airport food court Gate C22
Columbus airport – 2.4 GHz band
Birmingham BHM airport food court wifi
Dallas Love Field WiFi snapshot
San Antonio airport wifi – SAT Concourse B (American & United Airlines) Food Court –Free Wifi. Very good speeds. Measured over 50 Meg up/down with Ookla, over 10 Meg up/down with Speakeasy.net.