[perilunar]

> Before the Wright brothers, it was believed that powered, controlled, heavier-than-air flight was impossible.

Not by the many people around the world working on the problem, and their supporters.

Also, “powered, controlled, heavier-than-air flight” is exactly was birds, bats, and many insects do — it clearly wasn’t impossible. You need to add a couple more adjectives to qualify what the Wright’s achieved.