The Hoenn Region holds a plethora of Flying-type Pokémon, but I will only list the ones that can learn the HM Fly: Swellow, Pelipper, Crobat, Dodrio, Skarmory, Altaria, and Salamence. (I am not counting Tropius and Xatu beause they're not very useful)
Swellow
![Swellow](https://img.pokemondb.net/sprites/heartgold-soulsilver/normal/swellow.png)
Swellow is a solid choice, with stellar Speed and a decent Attack stat. He's able to learn some strong moves, has a good Ability in Guts and is available very early on. For a moveset, try:
- Fly
- Return/Quick Attack
- U-Turn
- Steel Wing/Roost/Quick Attack
(I'm assuming you don't care about Natures or EVs, but if you do I'll add them)
Pelipper
![Pelipper](https://img.pokemondb.net/sprites/diamond-pearl/normal/pelipper.png)
Another good Pokémon also available early on, Pelipper can function both as a fighter and an HM slave, learning Fly and Surf. He has good HP and Special Attack. Try this moveset:
- Fly
- Surf
- Shock Wave (move tutor)
- Ice Beam/Roost
Crobat
![Crobat](https://img.pokemondb.net/sprites/black-white/normal/crobat.png)
Crobat is an incredible Pokémon with a variety of moves. He also has amazing Speed and useable Attack, as well as powerful STAB attacks. This is a good in-game moveset:
- Cross Poison
- Fly
- X-Scissor/U-Turn
- Steel Wing/Roost
Dodrio
![Dodrio](https://img.pokemondb.net/sprites/black-white/normal/dodrio-f.png)
While often overlooked in favour of more powerful Flying-types, Dodrio can hold his own in-game. He gets wicked high Attack and Speed, as well as Fly (don't ask me how). Here's the recommended moveset:
- Fly
- Quick Attack/Return
- Drill Peck/Roost
- Steel Wing
Skarmory
![Skarmory](https://img.pokemondb.net/sprites/black-white/normal/skarmory.png)
A nice defensive monster to add to your team, although you already have Slowbro. Still, Skarmory is a positive addition to any team with his amazing Defense. Usually a Skarmory would know moves like Defog and Stealth Rock, but since in-game is usually hyper-offensive, I will suggest an appropriate moveset:
- Fly
- Steel Wing/Iron Head (move tutor)
- Rock Slide/Roost
- X-Scissor/Night Slash/Roost
Altaria
![Altaria](https://img.pokemondb.net/sprites/heartgold-soulsilver/normal/altaria.png)
Altaria possesses an incredibly diverse movepool, able to run both physical and special movesets. This, when paired with its decent bulk, make it a good choice for a Flying-type to add to your team (that, and it's a freaking cloud dragon).
Physical
- Fly
- Dragon Claw
- Dragon Dance/Roost
- Earthquake
Special
- Fly
- Dragon Pulse
- Moonblast
- Flamethrower/Ice Beam/Roost
(I would recommend using Altaria's Mega Evolution, but it isn't necessary.)
Salamence
![Salamence](https://img.pokemondb.net/sprites/black-white/normal/salamence.png)
And finally, the king of all Hoenn Flying-types, Salamence. He is a literal killing machine (or is that KOing machine?) that tears through all who oppose him...except Ice-types, be sure to have a counter for those.
- Fly
- Dragon Claw/Outrage
- Earthquake/Stone Edge/Rock Slide
- Crunch/Zen Headbutt/Fire Fang
Well, those are all of the viable Flying-types in OR/AS who are not Tropius, Xatu, Rayquaza or part Bug-type. I hope you're able to find one that works for you.