So, 5 years later in the future , aliens come from the Star System of Betelgeuse, where they have been mining an unobtanium/handwavium alloy. But they have problems with secure storage of this alloy, so they have shortlisted candidates to give some of it to. They choose planet Earth and announce on every means of comminucation ever known -
We, the Betelians, are giving you Unobwavium - an alloy which allows you to fly. Take 1 mg of it and you can fly for 1 h.
Hearing this, all the humans are like "YAY! I can fly!".
But wait!
When you take unobwavium, 1 year of your life is stripped off. Be careful, puny humans! Goodbye, say the Betelians and leave in their spaceship
What happens to the world? What are the good (and ill) effects of this?
EDIT - In response the @J_F_B_M, I have answered a few questions. There is a limit (around 1 ton a year) of this unobwavium. If you take more, everything is added (so if I take 2 mg, I get 2 h of flight and 2 years stripped off my life).