What if you found out that you are already late for your flight upon arrival at the airport? Worse, you have already checked in and passed the immigration! This happens even to the best of us. Calmly do these things:

1. Report the missed flight to the airport staff for decontrolling or proper exit at the airport. Although this is a very humbling moment, informing them of the incident will give you the opportunity to be escorted out of the airport legally. If you have made purchases, you have to declare them. If you have checked-in luggage, your bag will be released from the plane and will be returned to you. After ensuring that everything is okay, you will be joined by the airport staff to the arrival section, where you will exit.

2. Consider your options. You can opt for a second flight. Go to the ticket desk and inquire on the next available flights. Some airlines offer a "rescue fee" discount if you book a flight within two hours of the missed departure. If there are no available departures within the day, you can ask the staff to put you on the reserve list. However, do not just rely on that. See if other airlines have available flights. If you can't really find an immediate flight, plan on your accommodation for that day. You can use booking sites such as Trivago, Agoda, and Priceline for big discounts.

3. If it is not your fault, ask for compensation. Especially if it is the airline's fault, they must be able to assist you with this problem. If you are in the right, be prepared to show any evidence that would support your cause. Be as nice as possible when talking to the agent. Try to explain things in a calm manner.