There is a difference between check in deadlines and departure gates deadlines .
Please note each airline has its own deadlines, these are often indicated on your plane ticket or on your travel memo.
After this « deadline » ( latest check in time ) you will not be allowed to check in for your flight.
It's too late ! Your seat can be given to a passanger on the waiting list.
Some examples of check in deadlines with Air France at Paris Charles de Gaulle airport :
- 40 mins before departure for a short haul flight within France
- 60 minutes for long haul flights
- 90 mins for a flight to Africa (except South Africa 60 mins)
Once you are checked in, the departure gate deadline is the maximum time you have to get to the boarding gate.
Example with Air France at Roissy CDG :