If you’re delayed on your way to the airport because of a summer thunderstorm, you might think you’re out of luck. Most airlines now gladly charge you a full walk-up fare for the next flight when you don’t get to the gate on time — even if it’s for a reason beyond your control.

Here’s a secret: The so-called “flat tire” rule still exists in some places, notably Southwest Airlines. You just have to remind the ticket agent that it’s still there. And in some cases, you need to know what it’s called.

For example, at US Airways, it isn’t called a “flat tire” rule. It’s referred to as the “two-hour” rule.

This is from a US Airways insider, who retrieved the text of the two-hour policy from its reservation system:

A passenger who has missed their schedule flight based on unforeseen causes ie. flat tire, accident, traffic delays may standby without penalty or charges provided:

1. The passenger arrives at airport no later than two hours after departure of their confirmed flight, except if it’s the last flight of the day, in which case, they can standby on first flight next morning.
2. The passenger must standby on flights of same airline as their ticketed flight

The 2-hour rule is not to be solicited or referred as part of fare rule to circumvent voluntary changes. In-house exception made only when passenger has made an attempt to make originally scheduled flight.

In other words, US Airways employees must not advertise the rule to their customers. But they can, at their discretion, waive the fare rules and rebook a passenger on the next flight at no charge.

At a time like now, when summer thunderstorms are likely to cause massive flight delays, it’s good to know that airlines will cut you a little slack.

What’s not so good is that you need to know the secret password. Otherwise, you may have to pay for a new ticket.