Be careful! Most of the US airlines operate at 90%+ load factors and with a staff of 50,000+ there are always a handful of employees trying to travel on any given flight. With a ZED ticket you are the last to board. I've spoken with EK crew that were stuck for 2-3 days in places like JFK/LAX.
Might be a better deal to just buy a ticket. Virgin America, Allegiant, Spirit, Us Airways, Alaska, Jet Blue, and SWA sometimes have good deals on certain city pairs.