UFO??

Hello! Im not sure what I saw... But I'll tell it to you!
First, I were looking up in the sky, only sun, no clouds, no birds, nothing, very hot day... Then I saw it!
It was gray, and it were flying on very high, it has some kind of wings, but not bird's wings! It was FAST! But it flight like.. umm.. Well it wasnt clear flying, that think were stopping, continue, stop, continue, stop... but very fast stops... (Sorry im from Finland, its hard to tell those thinks on English ) I hope you understood...