If you fly with any frequency, it will happen. You think you’ve left plenty of time for yourself to get to the airport, but traffic, or a flat tire, or any of life’s little surprises gets in the way, and you just don’t make it.

You’ve missed your flight.

From the parking lot, you can practically see your plane climbing into the sky. And you swear you see the pilots waving at you.

It may feel like the end of the road, but there are secrets from the airlines themselves that can help you minimize the pain and inconvenience of not being where you’re supposed to be.

First of all, there is an unwritten rule called The Flat Tire Rule. The airlines recognize that oftentimes things happen outside of anyone’s control. How many of us have sat on an airplane for hours while waiting for some random thunderstorm to move or for a new crew to arrive? Do we get anything for those delays? A refund for our wasted time? Noooooo. So, if anyone should be sympathetic to our plights, it’s the airlines.

And they are sympathetic – to a point. If you can make a case that you were delayed due to a mechanical issue outside of your control, then your fare change or cancellation fee may be waived. This is huge, because last minute tickets can cost thousands of dollars.

So, how does this work? Well, it depends on the airline. And since the rule is generally unpublished, you will be hard pressed to find procedures on their websites. However, you can find much of this information from the travel experts at ThePointsGuy.com.

Read on for their most useful tips on the major American air carriers.

American Airlines

Ask about their unpublished Late Arrival Standby Policy, which allows passengers who check in within two hours of scheduled departure to fly standby on the next available flight that day only with no change fees.

Delta

Delta says they will apply a flat tire ruling when, “a customer who in good faith arrives [late] at the airport due to [an] unforeseen delay.” Ruling is left up to airport agents.

Southwest Airlines

If the passengers calls within 10 minutes of scheduled departure, Southwest Airlines can give the passenger full credit. Also, like American, Southwest Airlines will allow passengers to fly standby on the next available flight if the passenger arrives within two hours, even if the flight is the next day.

United Airlines

United’s flat tire rule will be put into effect after the passenger arrives at the airport within two hours of scheduled departure.

The most important thing to remember is you need the help of the airport agents. Make them want to help you by pleading your case calmly and honestly. If they believe you did everything you could to get there on time, all should work out to get you on your way.

But if you’re rude to them…it may not go your way.