Boeing Commercial Airplanes Group is developing a family of 747 derivatives for the large-airplane market. Included are the two models shown in this artist's rendering: the 747X Stretch, in the foreground, will become the world's largest 747, with seating for up to 522 passengers; the 747X, in the background, is slightly larger than today's 747-400 but will fly very long ranges. Depending on market interest, either of these new models could enter service in 2005.