Imagine you're flying across the country to visit your family for the holiday only to find yourself stuck in the airport halfway there because of "mechanical difficulties" on the part of the airline. Do you suck it up and wait for the next flight that they promise will be "in a few hours"?

If you are a savvy air traveller, you wouldn't. Rule 240, a well-known but still unpublicized rule governing airline conduct, can be invoked and the airline is required to put you on the next available flight to your destination, even if it is on a competing airline. If no flight is available, you are required to be put up in a hotel until one is available.

Now, this rule does not cover weather delays or air traffic problems beyond the airline's control.

The best thing to do is check your airline's "contract of carriage" and find Rule 240 on it. It is also a good idea to bring a copy of the contract with you on your flight just in case you have to invoke it.

Even with the rule, there are no guarantees, especially if you are flying a smaller economy airline. It's best to stick with the larger established airlines.