Safest bet is to "know before you go". Check the airport's website from home and they usually have posted instructions as to how to connect which include SSIDs. If they don't send them a nasty email about how dangerous it is not to publish such important information
For example:
http://www.panynj.gov/airports/jfk-w...tructions.html says it's provided by Boingo. Boingo's site (search hotspot directory for JKF) says SSID "Boingo Hotspot".
If you can't verify it before hand don't use it...