This question already has an answer here:
If a flight is delayed, and they announce in advance the delay, is the check-in time also delayed?
Say, at 13h, the flight, that was scheduled for 16h, has an estimated departure for 16h30. If in-person at the airport check-in time was 15h20, is check-in time 15h50 now?
Somehow this If I know a flight is delayed can I turn up late for check-in at the airport? answers my question.