AI 2518 then AI 2491 at Mumbai
Kolkata → Mumbai → Lucknow
Timetable, Mumbai time
11:20AI 2518 from Kolkata at the gate
11:15AI 2491 to Lucknow leaves the gate
23 h 55 apart on the timetable, overnight
AI 2491 leaves 23 h 55 after AI 2518 arrives on the timetable: more than half a day, so not a connection we count.