Thursday April 21 I plan to fly in to O'Hare from Zurich arriving terminal 5 at 15.45

I have a domestic connecting flight with United leaving at 17.50 from terminal 1

I will be travelling business on both flights and will only have hand baggage.

Is this gap sufficient? Would a United business (first) ticket offer priority lanes? Any tips?

Ohare has passport control kiosks, so things do move faster, then the tram to Terminal 1, then the security line, then the walk to your gate. 2 hrs is doable if you are ontime

ORD also has a separate lane for passengers with no checked bags. It's on the right, just before the arrivals hall and is faster than even the self-serve kiosks.

You should be ok, but won't have lots of extra time.

Is there a fast track security line for business/first class passengers?

I suspect the "fast track" thing depends in part on your airline, but probably yes if you're on UA or AA.

(I'm assuming you meant when you get to Term. 1 for domestic flight, not arriving customs/immigration at Term 5.)

Check this website for an idea of what you might be dealing with: http://www.ifly.com/chicago-ohare-in...ort/wait-times Note that it also has terminal maps, etc. If you haven't been to O'Hare before, Term. 1 has 2 gate-clusters/concourses (B gates and C gates) separated by a long tunnel with moving walkways. It's efficient, but the transit does add some time if your departure is from a C gate.