At the recent Paris Air Show, Airbus (OTC:EADSY) gave the world a look at its A380plus concept, a proposed upgrade of Airbus' struggling A380 jumbo jet. The A380plus would provide a double-digit improvement in unit costs, according to Airbus.

The main source of economic improvement from the A380plus concept is that it would allow airlines to squeeze even more seats onto each plane, but the main reason the A380 has sold poorly is that it is too big. In recent years, airlines have shown a strong preference for smaller widebodies like Boeing's (NYSE:BA) 787 Dreamliner. As a result, the A380plus concept is not likely to gain any traction with airlines.

A more efficient A380

Airbus says the A380plus would have a cost per seat 13% lower than today's A380. New winglets and other aerodynamic improvements would reduce fuel burn by 4%, while an optimized maintenance program would provide additional cost savings.

The Airbus A380plus would reduce operating costs per seat by 13%.

Airbus recently unveiled the A380plus concept. Image source: Airbus.

Most of the cost improvement would come from putting more seats on each plane, though. Airbus says that a smaller, relocated forward staircase would free up room for 20 more seats; replacing the rear spiral staircase with a straight staircase creates room for another 14 passengers; and moving to 11-abreast seating in economy and 9-abreast seating in premium economy would allow airlines to squeeze in 34 more seats.

Including some smaller changes, Airbus' proposed "cabin enablers" would boost the A380's capacity by about 80 seats, or more than 15%.

Emirates doesn't sound interested

The first red flag for the A380plus concept is that Emirates doesn't sound interested. That's a problem because Emirates is the only airline in the world that could be considered a big fan of the A380 right now.

Emirates CEO Tim Clark recently indicated that he opposes the changes to the forward staircase, which he thinks would reduce the A380's passenger appeal. He also opposes the 11-abreast seating concept. That isn't surprising, because 11-abreast seating would entail more middle seats, narrower aisles (which means more bumping into people in the aisle seats), and extremely little space at foot-height for the window seats.

These two "cabin enablers" account for more than half of the potential seating increase. Without them, the economic benefit of the A380plus would be significantly smaller.

However, Clark's main gripe -- and the primary sticking point holding Emirates back from ordering more A380s -- is the lack of orders from other customers. This is important because Emirates likes to retire its planes after 12-15 years. However, that only works from a financial perspective if there's a vibrant secondary market in used airplanes.

Right now, there doesn't seem to be much of a market for used A380s. Some of the first used A380s have hit the market this year, and the current owner is considering scrapping some of them for parts.

Who would want such a plane?

If Emirates is waiting for other airlines to make the first move before ordering additional A380s, then Airbus' jumbo jet is in bad shape.

Budget airlines like AirAsia X, Norwegian, and Scoot have been the fastest-growing long-haul carriers recently. They typically have point-to-point (rather than hub-and-spoke) business models, which makes smaller widebodies like Boeing's Dreamliner more attractive. Upgauging from a Boeing 787-9 to a massive Airbus A380 doesn't reduce unit costs all that much, while the big increase in capacity is sure to weigh on average fares.

Thus, the A380 hasn't made any headway with budget airlines. Instead, it has mainly been ordered by big national airlines that operate hub-and-spoke business models. Emirates operates the biggest international hub of any airline, so it's not surprising that it is the A380's biggest fan. It has ordered 142 A380s, accounting for 45% of the A380s delivered thus far and the vast majority of the remaining backlog.

An Emirates A380 aircraft

Emirates is the only airline that is a big fan of the A380. Image source: Emirates.

Other major operators include Singapore Airlines, British Airways, Lufthansa, Korean Air, Air France, Etihad Airways, Qatar Airways, and Qantas. For various reasons, none of these airlines seem inclined to buy more A380s, even with a double-digit reduction in operating costs that would mainly come from squeezing more seats onto each plane.

For example, Emirates' two main competitors -- Etihad and Qatar Airways -- don't drive enough volume through their hubs to justify operating large A380 fleets. Qantas' management has been blunt in saying that it doesn't have viable opportunities to deploy the remaining eight A380s that it has ordered (which have been deferred indefinitely). And while British Airways is interested in expanding its A380 fleet, it would only do so by buying cheap used aircraft.

In short, while Airbus may have found a way to reduce unit costs for future A380 buyers, it's not clear that there's any market for such a plane. The A380 remains a highly specialized aircraft, and few if any airlines need more jumbo jets than what they already have.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.