The airplane is one of the greatest mechanical inventions by christians, but is it the greatest of all time? The telescope is another good one, but I think airplanes outrank telescopes in usefulness. Of course the airplane would never have been invented if Carl Benz, another great christian inventor, hadn't first laid the groundwork. Orthodox christian Igor Sikorsky invented the helicopter, it has some improved functionality over the airplane, but some things are worse too. Robert Goddard was in the choir at his church, maybe that inspired him to higher things.