UA 225 then AA 9950 at Philadelphia
Denver → Philadelphia → Chicago O'Hare
Timetable, Philadelphia time
15:46UA 225 from Denver at the gate
13:01AA 9950 to Chicago O'Hare leaves the gate
21 h 15 apart on the timetable, overnight
AA 9950 leaves 21 h 15 after UA 225 arrives on the timetable: more than half a day, so not a connection we count.