Complex sentence: Ader's proponents have claimed that the Wright's early airplanes required a catapult to take off, however the Wrights did not use a catapult for their first flights in 1903, though they did for many flights in 1904 and later.
Split into simpler sentences: Ader's proponents have claimed that the Wright's early airplanes required a catapult to take off. The Wrights did not use a catapult for their first flights in 1903, though they did for many flights in 1904 and later.