BROUGHTON, UK—Like a cartoon space alien with a dome-like skull, an Airbus Beluga transport plane arriving from Madrid drops from the sky above this village 200 miles northwest of London and taxis to a stop with its front end tucked inside a large building off the runway. Its bulbous forehead pops open to disgorge massive wing panels—98 feet long and 20 feet wide—that will soon be assembled by sophisticated robots and about 800 people into the largest carbon-fiber composite wings now built for commercial aviation. MORE