We have a group traveling CLE-ORD-IST tomorrow. Current weather in CLE is thunderstorms, and though tomorrow's forecast is better, we'd like to be prepared if something goes wrong.

Our flights were purchased from and ticketed by TK, but the first leg of the journey (CLE-ORD) is on United (actually UX). Layover in ORD is about 3 hours, and we're on the last CLE-ORD flight of the day.

If something goes wrong -- weather, mechanical, or otherwise -- with the CLE-ORD leg, what happens? Who handles the irrops? TK doesn't have a presence in CLE, so would UA take over? Would they possibly reroute us (i.e., CLE-IAD-MUC-IST on UA, or something else on CO)?

Our group is about 12 people, split up into several PNRs. There are two 1ks in the group, both on one PNR.