KL 48 then KL 9955 at Schiphol
Chicago → Amsterdam → Brussels
Timetable, Amsterdam time
06:39KL 48 from Chicago at the gate
07:00KL 9955 to Brussels leaves the gate
21 min apart on the timetable
The last days
KL 48 and KL 9955 weren’t both flown 15 min to 12 h apart in the last 21 days.
Statistics from past flights, not live flight information. Always check times and your connection with your airline, and don’t base travel or booking decisions on these numbers.