If you have a transit in ORD, be sure to check its close enough to your arriving gate. As an example, I arrived at gate L4 which is in terminal 3. My connection to SFO was in terminal 2 gate C27. It’s very very far from L4. With only 25 mins between transit, I walked half way and ran the other half, and still couldn’t get there on time. Therefore, prefer to have the next flight close enough. If you fly American think twice before choosing United as next flight if you have very little in between flight time as United terminals are far. It was a lesson learned for me…