It all started with Seeing Eye dogs many decades ago, when physically-challenged passengers brought their trained pooches aboard. Now, when you're on your flights, you may see cats, birds and other allegedly helpful critters coming along in the cabin seats.

Now, with Delta and soon with many other airlines, those passengers who claim their pet raccoons or aardvarks help them make it through the flight must first show written proof. The animals must be qualified by training, health, inoculations and other requirements to do the support job. So, before you head for the airport with your helpful critter, be sure to check with the airline for the latest regulations