This African Grey had a bad cut as you can see on the wing. The feathers closest to the bird are cut, those are what your bird uses to slow his descent for a soft landing. If the bird gets startled and goes to flap he may CRASH HARD. You want your bird to be able to fly down safely, but not up. Many Avian Vets see birds because people cut too many feathers and the bird has to take a emergency visit to the vet to stitch him up.