I'm sure the original pre-domesticated chickens were reasonable flyers - far better than the fethered roasts which have now been bred.
I recall reading an article a few years back about some guy in the 1950s in England who kept his Tiger Moth in a barn shared with a flock of domestic fowl. One day whilst flying he discovered he had a rooster as stowaway in the empty front cockpit (appropriate term in this case).the rooster seemed OK with flying, until at about 2000ft he decided to hop onto the cockpit coaming to have a better look. This wasnt too good as he was swept away into the slipstream. Aparently he then descended gently to the ground crowing from time to time, but not particularly bothered. the pilots brought the Tiger Moth down as quickly as he could, afraid the bird was a goner. on landing he found the rooster wandering around quite happy. regardless of their flying ability, small animals and birds reach their terminal velocity very quickly, and hence dont reach the high speeds a human would. The pilot and a mate later incorporated a "rooster drop" in a routine they performed at a number of airshows, the rooster being quite happy about it all. Unfortunatley the Humane Society found out about it and insisted the rooster be given a parachute, which meant that it couldnt open its wings properly, nor walk around after landing, which stressed the bird quite a lot, so the Rooster drop was removed from the routine - it appears the society were unaware that birds were capable of flying!