Another episode in the romance of flight is on its last legs.

Jumbo jets, the double-decker, four-engine planes that more or less created the global aviation industry in the 1970s, have seen declining sales for years.  Airbus hasn’t won an order for a single A380 this year, the first time that’s happened since its maiden flight in 2005. Boeing has managed to shift four of its venerable 747s, but they’re all freighters. Unless things pick up in the second half, aggregate global sales of both models in the three years through December will total just 27 —  barely more than Pan Am’s inaugural 1966 order of 25 747s.

The latest nail in the jumbo jet’s coffin comes in the form of a stretched version of Boeing’s single-decker, twin-engine 777. The U.S. company has approached carriers including Emirates with a proposed design that would seat about 450 passengers, people familiar with its plans told Julie Johnsson and Andrea Rothman of Bloomberg News. At present, airlines that want to carry 450 passengers on a single plane can only use an A380 or a 747. The trouble is, few want to carry many more than that.

Proposed stretched 777 capacity is 450 passengers

The stretched 777 would compete head-to-head with Airbus’s biggest plane, which has irritated Boeing ever since it started encroaching on the 747’s territory a decade ago. Emirates’ smallest A380 variant carries 489 people in three classes, according to SeatGuru.com, while its biggest 777 model carries 427.

The shift has been in the works for a while. One of Boeing’s responses to Airbus moving in on the 747’s market has for many years been to tacitly question the role of jumbo jets altogether. The future of aviation lies in smaller, quieter and more fuel-efficient planes that can carry fewer passengers at greater frequencies between more destinations, the U.S. company argued.

“The vast majority of growth in air travel has been met by an increase in new nonstop markets (airport pairs) and by frequency growth—not by an increase in airplane capacity and/or size,” Boeing said in its latest 20-year market forecast. The average size of planes is, if anything, going down.

Airbus, not surprisingly, sees things differently. The growth of global megacities and congestion at the airports that connect them will inevitably mean rising demand for bigger planes, according to the European company’s own 20-year outlook. Planes owned by Middle East airlines are more than twice as big as those run by their North American counterparts, it says, none-too-subtly suggesting that Boeing’s philosophy may be no more than Yankee parochialism.

In truth, it’s hard to know which planemaker will be proved right. While years of $100-a-barrel oil have favored more fuel-efficient planes that can fly on two engines rather than four, crude is now trading south of $50. And if fuel-efficiency rather than capacity was the only issue counting against the biggest jets, it’s odd that Boeing and Airbus aren’t developing carbon fiber-bodied, new-engine models in that size class.

Perhaps in the long term Airbus’s view of the world will win out, and jumbo jet orders will resume their previous vigor. In the meantime, you’re still likely to find yourself on plenty of planes with onboard staircases. Qantas’s first 747-400 was in service for 25 years, while Iran’s flag carrier was still flying a 747 ordered before the 1979 revolution as recently as 2014, thanks to U.S. sanctions.

That’s little consolation for the big aerospace manufacturers, which don’t have the luxury of budgeting on horizons as lengthy as their market forecasts. Boeing, Airbus and their suppliers all have capital tied up in facilities for manufacturing planes that the world doesn’t appear to want. Unless orders pick up soon, it looks like the great age of the jumbo jet is dead.

This column does not necessarily reflect the opinion of Bloomberg LP and its owners.

To contact the author of this story: David Fickling in Sydney at dfickling@bloomberg.net.

To contact the editor responsible for this story: Matthew Brooker at mbrooker1@bloomberg.net.

©2016 Bloomberg L.P.

This article was written by David Fickling from Bloomberg and was legally licensed through the NewsCred publisher network.

Photo Credit: In this August 2, 2009 file photo, a British Airways Boeing 747 taxis away from Terminal 5 at London's Heathrow Airport. Mark Lennihan / Associated Press