It depends on what type of crystal. You may be accused of smuggling.
(Crystal would probably prefer her own seat)
You Use fly and just fly there
You can use fly anytime you are outside.
Assuming you mean the hm fly on Pokemon crystal, you get it from the lady out side of Cindawood gym.
Go fly
In Pokemon Liquid Crystal, HM Fly is given to you by an Aide in the Goldenrod City Department Store after you have received the Glacier Badge. You can then teach the HM Fly to one of your Pokemon to fly to different locations in the game.
If a fly has flown into your ear, tilt your head to the affected side and gently flush your ear with warm water using a bulb syringe. Do not try to remove the fly using objects like cotton swabs or tweezers, as this can push the insect further into your ear canal or cause damage. Seek medical attention if the fly is still stuck after attempting to flush it out.
liquid crystal isn't actually a real Pokemon game
If a fly goes in your ear, try to remain calm and tilt your head to the side to let gravity help the fly come out. Avoid using objects to try to remove it as this can push it deeper. If the fly doesn't come out on its own or you experience pain or other symptoms, seek medical assistance.
In Pokemon Crystal, the HM Fly can only be obtained after defeating the gym leader in Cianwood City. After winning the badge, speak to the woman standing out side of the gym. She will give the player Fly.
You get it from a girl in Cianwood after you beat chuck.
* firefly * fly
Chuck's Wife (in front of the gym) Will give you Fly after you beat Chuck