Gus the quaker zooms around the room constantly, following me as I go about my day and trying to land on my head no matter how much I discourage it (I wouldn't mind, except that he thinks all hair is meant to be plucked).
My new TAG, Boo, on the other hand, has all her feathers and appears to have a full range of movement in her wings, with no sign of discomfort when spreading them, but in the week I've had her, I've only seen her "fly" twice, once when she was spooked and once when she tried to climb a narrow shelf and slipped off. Both times she didn't so much "fly" as "break her fall in the direction she happened to be facing."
I don't think she's physically capable of gaining altitude, nor does she appear to have even minimal skill at turning or braking. She's 11 and I don't know anything about her background beyond the past six months or so, but I suspect that due to clipping, confinement, or a combination of both over the years, she never learned how to fly. She occasionally spreads her wings for balance, but that's about it, and she's afraid even to jump from one perch to another. If she can't reach it with her beak, she gives up.
I've begun encouraging her to flap, to slowly start building up some muscle, and I plan to teach her to fly if birdly possible, but I fear it's going to be a long road.