Redefining the 757 replacement: Requirement for the 225/5000 Sector



Airbus and Boeing had been evenly matched with the A320 and 737NG families until December 2010, when Airbus launched its re-engined neo. Boeing dismissed the Airbus product until officials were stunned by the decision of legacy American Airlines to abandon its exclusive reliance on the 737 and signaled it was ready to place a large order for the A320neo family. Within 48 hours, Boeing launched the 737 MAX.

While the 737-8 and A320neo remain the heart-of-the-market, the 737-9 proved significantly less capable than the A321neo, which quickly outsold the 9 MAX by a factor of 2.5 to 3:1, depending on any given year. Boeing’s position with the 9 MAX got worse when Airbus told Leeham News and Comment October 21 last year that they were working on a longer range version of A321neo we subsequently called A321neoLR.

Although the heart-of-the-market 737-8 trails the A320neo in sales, the MAX program nonetheless remains highly successful, with more than 2,600 ordered and backlogs running to 2020 and beyond. Still, there was a clear product gap above the 737 MAX and A320neo which is Boeing territory with the 757. Boeing’s discussions with the airlines were focused on launching a 757 replacement which subsequently could be waterfalled down to replace 737 MAX in due time.

The Airbus launch of A321LR changed all that.

Suddenly this hole was not plugged by Boeing and at their leisure, archrival Airbus pulled a coup and moved the goal posts in the segment that Boeing saw as their turf.

The reaction was a mix of disbelief (the A321LR “doesn’t work”) and “nothing has really changed because this is a small niche and we are focused on the center of the single aisle market where our MAX 8 is the best product.”

Our Market Intelligence indicates Boeing internally takes the A321LR much more seriously than its public posture. Airbus can undertake even further improvements of the A321neo. It’s not widely discussed yet, but Airbus is considering what the market calls an A322, a stretched, new-wing version that removes any doubt about a 757 replacement and further addresses 200-250 seat, 4,500nm requirements.

Boeing is toying with a further improvement of the 737-9, with the working title  737-10, but this would be an extreme makeover with considerable challenges. Everyone is now second guessing what might come out of it all.

Part of our reveal of A321LR was that we could see in our performance model that A321neo could be extended further. We also modeled Boeing’s capabilities to follow suit with 737 MAX9 and a 757 MAX, we have covered why neither works in the above linked articles.

Before we started the 757 replacement article series we checked out what a low priced 767-300ERW could do versus the 757 in this segment. The result was that it could not compete, it wouldn’t be cheaper than a 757-200W and now we are 25% below that in fuel costs with A321LR. We have also checked what a re-engined 767-200 would give. It is smack-on the seating capacity that Boeing is saying the airlines are now asking for, but the economics don’t work for this 30 year old aircraft design.

Present and derivative alternatives, how they stack up

To give a base level for our discussions of the market segment and what is required to make a new design work, we need to understand where present and discarded players play. From this we get the baseline against which a new design can be measured. Figure 1 summarizes the performance of all discussed aircraft over our transatlantic mission, 3400nm. The table measures all important parameters for the aircraft against our normalized seating. This functions as an apples to apples equalizer for the different size aircraft.

Article 1 main table2

Figure 1. Table showing main data and efficiency of A321LR, 737 MAX 9, 757-200, 757 MAX, 767-200, 767 MAX and 787-8. Source: Leeham Co. Click on table to enlarge it.

With this equalization one can draw a number of conclusions from Figure 1. The present re-engined single aisle aircraft are very efficient. Fuel consumption per seat for any new design must be at least 10% better than these, therefore at least 0.0090 kg per seat and statute mile (Statute mile is the standard for such discussions in the airline industry). We can see that today’s 757, even when equipped with engines only available in 2020 (757 MAX with GE9X technology engines) still lacks the present single aisle aircraft in efficiency; it has to low aspect ratio wing and to high wetted area per seat, 116%. It is the beefy wing which is the culprit.

As we go to two aisles, things get worse. Efficiency for a 787-8 is 10% worse per seat flying this distance, a not too uncommon mission length for a 787-8. The 767 is outclassed by more than 30% and even if we equip it with the engines from 747-8, the GEnx-2B, and add the 767-400ER raked wingtips to improve wing aspect ratio, a test configuration we called 767 MAX, this only lowers the deficit to 22%. From this we understand that going dual aisle for this segment is a real challenge; wetted areas are around 40% larger per transported passengers and empty weights follow suit.


The normal OEM two class capacity for any new design shall be between 180 seats and 240 seats to cover any space not covered by A321LR and 787-8/A330-800, in our more demanding normalized ruleset (business has 60 inch pitch instead of the OEMs 36 inch) this would mean 160-230 seats. For Boeing it will be an advantage if a design can cover down to the present space for 737 MAX9, as it is not doing so well against the A321neo.

A problem area for a new design will be the cargo side. The most common container is the LD3, which only fits in the normal two abreast in the cargo pits on a cross section the size of A330  or 787. Below that the next common format is LD3-45, which is the container format for A320 series. Any new single and dual aisle that would have a cross section diameter below A330 will be using that cargo format.

Market requirements

With this background on what is available and the proliferation of these aircraft in the market we can start to formulate the requirements for a clean sheet design.

Covered market

The aircraft shall cover the market from 180 to 240 passengers (OEM rules) with a range of 5000nm, according to Boeing’s research. The covered passenger range is not too difficult to define. The present single aisle only delivers a realistic 180 passengers in a typical OEM dual class layout and the next modern aircraft is the A330-200 or -800 and 787-8 at 240 passengers in a two class layout.

The covered range needs more of an explanation. Presently the 757-200W and A321LR covers a range up to 4,000nm. This is with an alternate within 200nm from the destination and no wind on the sector. When bad weather at the destination area is added and prevailing westerly winds on the Transatlantic crossing, 5,000nm is needed to avoid frequent tech stops for refueling (there are frequent 757 tech stops right now due to the bad weather on the US east coast).

The 5000nm is also the range needed to cover Southeast Asia with necessary reserves, tying areas like main land China with Australia and Hong Kong with Middle East.

Market size

Much has been written about the differences between Airbus and Boeing regarding the 757 replacement market. Airbus estimates there being a market for about 1,000 A321LR whereas Boeing points out that the 757 that is being used for long and thin routes are less than 100. The 757 sold in total 1049 aircraft whereof 919 were the long haul capable 757-200 and 55 were the longer 757-300. To this one should add the smaller 767-200, -200ER and A310 as this covered the segment 200-240 passengers in two class seating up to ,6,000nm in range. There were a total of 500 767-200s and A310s sold over the years; most have been retired.

Any clean sheet aircraft would cover the market from 2025 at the earliest. By that time the passenger-mile market has doubled and the number of aircraft serving the market increased by 60%. It would therefore be realistic to estimate the 180-240 seat market at around 2,300 aircraft. Airbus 2014-2033 market forecast postulate a delivery of 3,700 aircraft in the 210 seat segment but it is unclear if that includes A321 deliveries. Boeing divides the market differently, with the 200-300 seat segment called small widebodys where they forecast 4,500 aircraft delivered over the 20 years.

All in, a market of 2,000-2,500 aircraft is a realistic estimate for clean sheet aircraft covering 180-240 seats.


The single aisle A321neo and 737 MAX9 are highly efficient aircraft, both around 25% more efficient per seat than the 757 and 33% more efficient than 767. Unfortunately for Boeing, the MAX9 cannot be stretched any further neither in range nor passenger capacity without major redesign of the wing and undercarriage and the narrow fuselage is probably not worth the investment. A re-engine of 757and 767 cannot close the gap.  Wetted areas, wing aspect ratios and empty weights are just too un-competitive for any new engine to close that gap. This leaves clean sheet designs as the only possible replacement and complement to close the gap to the next segment, 787-8 and A330-800 at 240 seats. In order to compete with A321LR, a clean sheet design will have to beat the per seat costs of A321LR paired with a longer range, preferably with 15%-20% on operational cost but at least 10%-15% and 1000nm in range.

This would have to be manifested in fuel costs but also maintenance costs and utilization where ground handling time will be one way to increasing the available passenger kilometers that the aircraft can perform per day.

In our next article we will look at how such improvements can be achieved and where the optimization of the ground handling would drive a cross over between a single and dual aisle solution.

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