How do I train my 3-year old dog to pee on a pee-pad?

In a month, I will be flying to Arizona from Florida with my 3-year old Chihuahua Terrier mix. Now it is a 4 hour and 45 minute flight. I have been reading up on tips and lessons on flying with dogs in cabin, with you on the floor. Because I can't leave the airport whenever my dog needs to go to the bathroom, I have considered the idea of pee pads. My dog does not usually pee on pads, she goes outside. I want to teach her that its okay to pee on the pad, but don't want her to get used to it because she won't be doing it when we get home. Please any suggestions would be great!

Added (1). Because of all the answers I have been getting, I want to apologize. Obviously it wasn't okay to assume my dog could just forget what I thought her about gong to the bathroom on a pee pad. But because you guys don't know my dog, you can't assume so wouldn't be open to the possibly. And second, if any of you read my actual question and additional information, you would know that I asked for suggestions on how to get her to go to the bathroom if its an actual EMERGENCY.

All you will do is confuse your dog. They should be more than able to hold their liquid for more 5 hours so when you get ready to leave, you can take your dog out to relieve himself and he should be good until you get to wherever it is you're going. All you are going to do is tell him it is okay to p*ss in the house when you get back home then you will be on here whining about THAT.

You don't. You potty her before boarding, and after your have reached your destination.
Limit water before and during the flight.
She will be in her crate the entire time and won't be allowed out.

You don't. Who told you you can't leave the terminal? Yes, you'll have to get in line again, but I'm familiar with flying with dogs, and this is not an issue.

Like other people have said, you can't temporarily train your dog to do something then expect them to forget it.
Some larger airports have specific doggy bathrooms.
Nobody is forcing you to stay inside the airport. You can leave, you just have to go through security and all of the standard boarding procedures to get back in to the terminal.
You might consider getting a patch of plastic grass. Put this down in the yard, and any time your dog goes on the plastic grass, give tons of praise. Its plastic, so its easy to rinse and clean in a bathroom. So at the airport, put the patch of grass over the drainage grate in the family bathroom, and let your dog pee on it. Because its over the grate, it will be easy to clean the floor too. Or you can put the grass on top of a pad. Then pick up the grass, clean, and put it back in your bag. Then when you get to your new place, put the plastic grass in the yard and leave it there.
This is for when you are at the airport, not on the plane. Once she is on the plane, it doesn't matter if its an emergency, you can't open the door and she will have to go in her crate. This is why you limit water before and during the flight.

By taking your dog out as close to boarding as you can and limiting water it should not be a problem.
Put an absorbant pad on the bottom of her crate if you are concerned.

Many airports have an area for dogs that are traveling in cabin to relieve themselves.

Do you have a layover? If not 5 hours or so is NOT that long that your dog can't hold it. This one time using a pee pad won't teach it to go in your house but she likely won't know she's supposed to go on it so what's the point?

I do hope you've reserved the spot for her on the plane? You can't just show up and bring a dog on board. You also will have to go to your vet no more than a week before your flight and get a health certificate from the vet which means ALL shots must be current.

Just don't… If it's already properly housebroken, make sure she has completely eliminated outside beforehand, a healthy properly trained dog should be able to hold it, should she have an accident, then just clean it up.