[Nikitta34]

Wow... harsh words on this thread! I fly with my dog as a service animal so the paying/stealing thing isn't an issue for me, but after a horrific experience of getting an airline to recognize my dog as a service dog, I decided to just take Meg on the plane for my return flight (without checking her in at the check-in counter). It was a short 2-hr flight and I kept Meg in her carrier the whole time. I had no issues getting through security (I carried Meg through and put her carrier through the Xray machine), no issues getting on the plane, and no issues during the flight. I've never flown on an airline that marks "pet" on your boarding pass, but that's not to say that some airlines (or even some airports) require this.

All that being said, here are some reasons you might not want to do this:
1) If you get caught, you will either be forced to buy a ticket or --- if the in-cabin dog limit for the flight has been reached, be forced to take another flight, perhaps on your own dollar.
2) Stealing/breaking the law/moral argument
3) Your dog will not be on the plane's roster. Heaven forbid there be an accident or your dog gets lost, there would be no record of him on the flight.
4) The chance that your vacation/travel time will be ruined due to you not being able to get on the flight.