Found and Explained Official on MSN

Why Boeing never built its double-decker 747X

Boeing’s 747X was supposed to answer the coming demand for giant airliners, with proposed versions carrying 400 to 650 ...
Flightglobal

Engine treatments to be priority for 747-400X upgrade package

Boeing is preparing a package of improvements for the 747-400 that will be unveiled at an operators conference later this year. Almost 30 alternative configurations are being studied, ranging from ...