Chickens can't fly

It's an often repeated piece of trivia that the longest ever recorded chicken flight is thirteen seconds - apparently the furthest flight was 301.5 feet. I can't find what type of chickens these were but I think Millie & Katie are warming up to take the record. They love to fly up on to me especially if I have some grain. I have also found them up trees, on the roof of the cottage and on the back wall. On one occaision Millie took off from the back wall at a steep angle until she was way above my head - I would guess between twenty and thirty feet. She then splayed out her wings and not entirely gracefully dropped down by my feet. We have decided not to clip their wings as they seem to like flying and have so far stayed within the back garden. I guess they have a better chance of escaping predators with intact flight feathers.