I am going to connect from UA OKC-IAH (UA 5278 in B) to D and Lufthansa.
It should be around 1hr 30m from arrival to departure.
Since there are no smoking boxes or lounges in IAH, can I leave B for a cigarette, re-clear security in B then transfer to D? Or would I need to take the underground train, and clear security in D?
Or, should I go to D, look at the security line and see how it looks?