My girlfriend flies her cockatiels outside;

https://www.instagram.com/budgiebrigade/

If you have questions for her I can ask her, but I'll try to tell you what I know.

She did lots of this inside first, making the bird fly away and fly back for a small amount of food.

https://www.instagram.com/p/BfQ_BB1Fgl7/?taken-by=budgiebrigade

Then I built a large outside cage out of 12 pvc pipes arranged in a cube with netting over it. She did the same thing but outside so the bird can experience wind, sky, noises, and seeing wild birds.

https://www.instagram.com/p/BlQgreGlP_4/?taken-by=budgiebrigade https://www.instagram.com/p/BkV0u3JAdMA/?taken-by=budgiebrigade

After they were really good at it, she did perch thing no cage.

https://www.instagram.com/p/BlGgm0ggMRg/?taken-by=budgiebrigade

Covered areas away from noises are good, like a path under trees. Get them used to a tree and a small area first. Big chance something spooks them and they will fly up into a tree for a couple hours. Have binoculars. By this time they should be extremely bound to you and your whistle sound, used to returning you noises, so even though they are scared they will not go out of range of you. It's always dangerous to free fly and there's a high chance you could experience loss at least once.

https://www.instagram.com/p/Bn1N_6YHmQl/?taken-by=budgiebrigade

This is him hauling ass through the air now.

https://www.instagram.com/p/BoC-cZvlokw/?taken-by=budgiebrigade