A good flying type may be a Golbat, which can be found around middle-late game at level 33-36. This can learn Fly and can be a great addition to your team. It has fast stats and a good attack and evolves into Crobat with full happiness.
You might also want a Pidgeotto. It can be found in the Safarai Zone: Area 2 at level 30 with DexNav application. It will later evolve into a Pidgeot, a good Pokemon with a solid Attack and Speed. Mega evolving it isn't necessary in Omega Ruby .
Altaria has a good Sp. Def and can be more of a tanky flying type. You can catch it as a Swablu at level 16-19. Salamence is also a solid pick for a flying type as it has amazing Attack and Speed. You can get it as a Bagon in Meteor Falls at level 37-40. You do not have to mega evolve these either.
Astronautical will put up some good movesets and stats for these Pokemon.
I hope I helped!
Oh yeah your team is good so far. Remember to use the Shiny Beldum event! You might also want to consider getting a Manetric for your team. Just try to vary your types among your Pokemon team.