Who invented the first airplane

It depends on what you mean.

If you mean a motorized heavier than air kite, the the Wright Brothers did. The flight took place on December 17, 1903 at Kitty Hawk North Carolina.

If you mean just lifting something whose density is more than air above the ground, then the Montgolfier brothers succeeded in doing that in 1783. It was tethered (tied down). A short time later, two other Frenchmen flew an untethered hot air balloon that was free to roam.