Redefining the 757 replacement: Requirement for the 225/5000 Sector, Part 4.

By Bjorn Fehrm

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08 March 2015, c. Leeham Co: In the third part of the article series around the need for a more capable solution for 180-240 seats and 5,000 nautical miles, we compared different clean sheet single and dual aisle aircraft to the Airbus A321LR and Boeing's 787-8, the two aircraft that form the border to the segment.

We could see that a single aisle aircraft started to have trouble with weight at around 220 passengers using our normalized seating rule set. This would with normal OEM seating rules be around 230-240 passengers. At the same time the dual aisle aircraft becomes stronger the more seats one assumes. The reason is their thicker fuselage, Figure 1, lends itself better to aircraft which passes 50 meters/160 feet in length.

MOM cross sections2

Figure 1. Cross sections for our studied clean sheet designs; NSA6 (New Single Aisle 6 abreast), NLT6 (New Light Twin 6 ab.) and NLT7. Source: Leeham Co.

Their advantages in boarding and deplaning then starts to outweigh their disadvantages in weight and drag. This trend is explored further in this part where we add Cash Operating Cost, COC and Direct Operating Cost, DOC, to the analysis.


  • The trends seen for NAS6, NLT6 and NLT7, our Middle Of the Market, MOM, models in the segment 180 to 240 passengers gets further reinforced when we go to COC and DOC.
  • A factor supporting this is the broader spread of fixed and semi-fixed costs over larger aircraft seat numbers.
  • Another is that the shorter ground turn-around time for dual aisles increases the utilization for the aircraft, once again forming a broader base for fixed and semi-fixed costs.
  • Introducing CFRP for the fuselage brings clear gains in weight and therefore operating costs. Key for its inclusion in the MOM designs will be the manufacturing advances that will have been made by 2025.

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