UA 923 then AA 9600 at Heathrow
Los Angeles → London → Chicago
Timetable, London time
13:30UA 923 from Los Angeles at the gate
13:00AA 9600 to Chicago leaves the gate
23 h 30 apart on the timetable, overnight
AA 9600 leaves 23 h 30 after UA 923 arrives on the timetable: more than half a day, so not a connection we count.