HM fly

Fight the rival at route 119 and he/she will give you fly.

On bicycle road, there is a building it that prevents people without bikes to enter,this is the northern building (this is also where a snorlax was). Cut down the tree near to the place and go through the opening. There should be tall grass and a couple trainers there. Enter the building to the left and an old man in there. Continue and you should reach a house, go in and a girl will say not to tell people about her secret hiding place. She will give you HM fly.

On route 29, where the Snorlax is sleeping, cut the tree, you'll see a couple that will battle you. Get pass them and go into the house to the left. A girl gives you HM Fly

Go west of Celadon City, and blow the pokeflute so that Snorlax will wake up, and move. Then cut the small tree near you, and proceed through all the buildings, and you should be above the cycling road area. Continue heading west, and you will come upon a small house. Talk to the girl inside of the house and she will give you the HM for fly.