VS 21 then UA 4274 at Dulles
London → Washington → Dayton
Timetable, Washington time
17:40VS 21 from London at the gate
17:25UA 4274 to Dayton leaves the gate
23 h 45 apart on the timetable, overnight
UA 4274 leaves 23 h 45 after VS 21 arrives on the timetable: more than half a day, so not a connection we count.