VS 747 and a UFO? (or fake?)

Just seen that this has "gone viral" - possibly a drone or can they fly that fast to overtake a 747 on take off? Or a fake?

https://www.youtube.com/watch?v=NSu5P3oY-OU

Well it is a UFO because it's an Unidentified Flying Object.

But does it have little green men inside? No. It's another plane.