The good news first: Airline interest in the proposed New Midsize Airplane (NMA) that Boeing is starting to develop from scratch and that Airbus is looking at responding to is huge. In a joint Aviation Week/Bank of America Merrill Lynch survey, 78% of respondents said they were interested in buying such an aircraft. In a market that is currently notorious for not placing many orders at all, that is a very significant number. Airlines also not only want the aircraft, they want it fast—around two-thirds would ideally like to take delivery of it by 2021, years before the earliest realistic entry-into-service dates the manufacturers can offer.

But the survey, published ahead of the 2017 Paris Air Show, also makes clear how difficult it will be for manufacturers to get right definition of the aircraft and that it is not a single aircraft they are looking at, but a family with different range and seating versions. Airline requirements could trigger a fascinating strategy play that not only involves future designs but also includes current product lines: The Airbus A320neo family that controls around 60% of the single-aisle market, a position it appears to be able to hold for the foreseeable future, and the Boeing 737 MAX, the relative weakness of which at the top end Boeing is trying to address through the launch of the 737-10.

The middle of the market, sitting between true long-haul aircraft and the single-aisles, has always been a tricky segment to address. Airbus started out as an aircraft manufacturer in what arguably is the most difficult part of the portfolio. The A300 and A310 were not real successes. The one true success in the space was the Boeing 757-200; the 767 and A330 exceeded the missions for which they were planned. The A321neo and the A321LR, however, look like they are getting closest to where the 757 left off.

What airlines are asking Boeing and Airbus in the survey puts the OEMs in a difficult position: The vast majority of respondents (90%) want fewer than 250 seats in a two-class configuration and up to 5,000-nm range (76%). A significant percentage of respondents (24%) want even more than the 5,000 nm. Two-thirds of potential future operators also expect a composite fuselage and composite wings. In other words, they would like an aircraft that is not too different in size from today’s narrowbody families but has a lot more range.

That is a problem for the airlines' suppliers. If they follow their customers’ requests, they seriously risk either cannibalizing their current narrowbody offerings or making it harder to turn a successor into a commercial success—and they likely risk both. Boeing not only faces the challenge of having to develop an aircraft similar in size to the 737 that is different enough to address different segments, it seems more or less committed to building a small 767-like widebody with much better economics than the 1980s-era design. But the smaller the aircraft becomes, the more difficult it will be to both keep widebody features and sustain narrowbody economics. Engineers are working on sophisticated designs that, Boeing says, make both possible.

But do customers even want a widebody? The survey does not deliver a clear answer. Only 51% of the airlines responding to the survey would consider a small widebody if it fits into existing gate infrastructure. That is not necessarily always a given if manufacturers at the same time take the range requirement seriously, which would then likely mean a large wing. Of course, the wings could become an issue even for a long-range narrowbody at some of the single-aisle gates at dense airports.

At the outset, Airbus appears to be in a more comfortable position. The A321neo and its long-range (LR) version seem to have about the right size for most operators, and being too small is not as serious a problem as being too big. On the other hand, the survey shows that Airbus is not there yet, in particular as far as range is concerned. More work needs to be done on range, as the A321LR as currently proposed reaches only slightly over 4,000 nm. As part of the A321neo "plus-plus" project (part of a broader initiative to modernize the A320neo family), more capacity is under consideration, but more importantly, more range has to be designed into the aircraft. Boeing knows the 737-9 and -10 are not the answers because of the range limitations. That’s where the New Midsize Airplane comes into play.

And the market seems ready for it. While 60% of the survey respondents say what they have heard about the Boeing project meets their expectations, only 40% say the same about the “A322neo,” the stretched and upgraded A320neo family addition Airbus has been looking at. Now all Boeing has to do is to get the design right.