Delivering the mail as quickly as possible generated a lot of competition and some innovative designs. One variant of the Short Empire flying boats was the strange-looking Maia and Mercury. It was a four-engined floatplane "Mercury" (the winged messenger) fixed on top of "Maia", a heavily modified Short Empire flying boat. The larger Maia took off, carrying the smaller Mercury loaded to a weight greater than it could take off with. This allowed the Mercury to carry sufficient fuel for a direct trans-Atlantic flight with the mail. Unfortunately, this was of limited usefulness, and the Mercury had to be returned from America by ship. The Mercury did set a number of distance records before in-flight refuelling was adopted.