I believe the OP was referring to Pokemon that can be caught pre E-4.
The Pidove line is a decent choice, the the lack of good STAB moves way leave something to be desired.
Sigliph is an excellent choice, though the rarity of finding one may prove a challenge. It gots a great, speed, special attack, & a decent movepool so it doesn't really slow down until post-game.
The Aaken line is a great choice due to the fact that it positively rips up the E-4 with its convenient movepool. Once It evolves to Archeops, expect it to completely make up for its ability. Only Archeops will learn fly though.
Tornadus & Thundrus are decent flyers, though they'll e just as useful as the next guy when it comes to the E-4. Be aware that they level up very slowly though.
I got a Dream World Staravia in my game and used that to dominate the first part of it (leading up to the fall of...that awesome place).
Failing that, if you're patient enough to find Sigilyph (at the Desert Resort), I'd suggest that one. It has excellent Special Attack and Speed and learns Air Slash through level up. Plus, Magic Guard prevents residual damage, so you don't need to worry about status conditions (although they're not overly common in the Elite Four). Plus, I think it's more worthwhile than trying to get a Woobat's happiness to max out.
Well a good flying type pokemon should be Rufflet or its evolved form Braviary it evolves at lvl 54. I picked this as my flying pokemon from Route 10 and its Physical Attack is its best stat and Fly is a Physical move so you can use it as a travel pokemon or a nice flying type attack but the problem is its only obtainable in Pokemon White Version not Pokemon Black Version and it is only found after the Last Gym Leader from Opelucid City which are Iris(White) or Drayden(Black) if you have Pokemon Black Version you could get Vullaby or its evolved form Mandibuzz it evolves at lvl 54 same as Rufflet and Braviary from Pokemon White Version and you can use Fly on it for traveling or just for battling those are my best flying type pokemon sorry you cant get them earlier but you can Trade with me on my Pokemon White Version my FC is 0690 9565 3031 name Ely I give out Rufflets and Vullaby or if you want me to train and evolve them to their evolved forms give me a shout and tell me if you want them
I'd say the best pure bird pokemon (normal/flying) from G5 is Braviary. Unfezzant's stats and moves don't match up well, and Vullaby (and its evolutions) have terrible stats and moves across the board.
Other than that, only Ducklett, Sigilyph, and Archen are really worth consideration. They are Water, Psychic, and Rock respectively. While all are good, the question is more about what your particular party needs.
Or, if you don't need a flying pokemon in your party, but you still want to fly, there is one option: Gollett. This Ground/Ghost can...somehow... learn Fly. Seriously.