Some small airports require you to check in a minimum of 30 minutes before departure. This is true in many airports in central MN where the same TSA people examine your checked luggage and also run the security screening at the gate for carry on luggage. They are adamant about closing check in 30 minutes before departure. Once I saw a family of four arrive at the airport 15 minutes before departure. I could not believe it myself. The agent said that they could put the passengers on the plane but their luggage would have to wait until the next day (it was the last flight out for the day). They decided to drive 2-1/2 hours to MSP and fly from there.

I have learned to never cut it close, especially at small airports (where your thinking might otherwise be that you can show up very shortly before departure which is not true).