Answer:
I am one small little piece of paper yet sometimes hold lots of value. I am all you need to get in to big events but will cost you. I am an important part of travel. And if lost you're not coming.
When set loose I fly away. Never so cursed as when I go astray.
What is always coming but never arrives?
What happens when you throw a green stone into the Red Sea?
They come at night without being called and are lost in the day without being stolen. What are they?
When is it bad luck to see a black cat?