"In terms of impressive technology, great capacity, great economics ... (the 777X) does sadly make the 747 look obsolete," AeroDynamic Advisory managing director Richard Aboulafia said.
Nevertheless, the latest 747-8 version is set to grace the skies for years, chiefly as a freighter, having outlasted European Airbus' double-decker A380 passenger jet in production.
This week's final 747 delivery leaves questions over the future of the mammoth but now under-used Everett widebody production plant outside Seattle, while Boeing is also struggling after the COVID pandemic and a 737 MAX safety crisis.
Chief Executive Dave Calhoun has said Boeing may not design a new airliner for at least a decade.