Boeing showing 737-8ERX concept in response to A321LR

By Scott Hamilton and Bjorn Fehrm

March 12, 2015: Boeing is showing some airlines a concept it calls the 737-8ERX, a long range version of the 737-8 MAX, in response to the Airbus A321LR, Leeham News and Comment has learned. Sources within Boeing confirmed the concept but Boeing Corporate Communications did not make someone available for an interview. A spokesman said in an email, “Boeing studies many advanced concepts, innovations and technology. However, just because Boeing studies a particular concept or technology does not necessarily mean that we will be introducing that airplane or concept in the near future. Boeing makes decisions based on market and customer demand.”

737-8ERX Spec

Figure 1. The Boeing 737-8ERX concept. Boeing photo, modified by Leeham Co., based on information from Market Intelligence. Click on image to enlarge.

In our article series around A321LR we concluded that Boeings 737 MAX 9 was not a good base from which to launch a long range 737, it could not be stretched in take off weight due to rotation limitations. Better would be to upgrade the take-off weight of MAX 8 for longer range, it can carry the extra fuel tanks needed and is not rotation limited in the same way.

As happened with the A321neoLR (we pointed to the possibility of the concept and Airbus was indeed working on it) Boeing now shows selected airlines a higher gross weight 737 MAX 8, Figure 1. In contrast to Airbus, which beefed up the A321neo to form the A321LR, Boeing is apparently using a concept they developed for the Navy 737 derivative, P8 Poseidon. They grab in their LEGO box of 737 components to form the 737-8ERX with minimal additional development.



Boeing’s 737 MAX, like the Airbus A320neo family, are limited in how far they can fly by the fuel their slender wings can hold. Airbus therefore adds up to three additional center tanks (ACT) to give A321LR a range of 3900nm. Boeing’s 737 also needs additional center tanks to be placed in the cargo bays to fly further. This extra fuel cost weight and to avoid that passenger seats have to be blocked with full tanks the max gross weight has to be increased in parallel with installing extra tanks.

Increasing max takeoff weight (MTOW) of an aircraft touches many components. If the extra weight is restricted to cater for more fuel, it requires “only” the beefing up of wings, landing gear and fuselage center section. For A321LR there was no stronger such parts to use. For 737-8 there was. Boeing proposes increasing the MTOW of the -8 to the -9 values and then uses its wings, landing gear and center section to cater for the increased weight.

Figure 2 shows the center section 44 for 737 MAX 8 and 9 where the latter has thicker gauge materials.


Figure 2. 737 center section 44 in manufacture at Spirit Aerostructures. Source: Southwest Blog. Click for a crisp view.

To this is bolted lightly modified front and rear sections of the -8, modified for interfacing a -9 center section and carrying the extra center tanks in their cargo area.

As the aircraft will take-off and fly with higher weights, it will have revised software in the Flight Management Computer to account for higher weights and modified flight characteristics. By using the MTOW from the -9 the extra fuel can be filled without weight becoming a limit. Combining that with max landing and max zero fuel weight from the -8 minimizes the changes needed in the -8 parts. Empty weight will land between that of -8 and -9. As the -8`s fuselage length enables ample take-off rotation, the 737-8ERX will use less runway then 737 MAX 9.

737-8ERX Range_1

Figure 3. The 4,100nm range is based on our assumptions in our proprietary modeling. The shorter ranges use stronger headwinds and other assumptions. Source: Leeham Co., Great Circle Mapper. Click on image to enlarge.

We have entered the values for an -8ERX in our performance model. Out comes a range of around 4,000nm when using two extra tanks and a configuration with 150 seats in Business, Premium economy and Economy. A major point for Boeing will be the retained family commonality for all MAX variants, with the long range ERX not breaking with this tradition.


Entry-into-service is discussed as 2020-21, up to two years after the A321LR. This is late and will limit the ERX’s market capture in the single aisle long range market. The ERX also carriers significantly fewer passengers than the A321LR. In our previous analysis, using the cabin configuration of 169 seats for United Airlines on its Boeing 757, we concluded the A321LR would seat 164 and the 737-8 would seat 136.

We also calculated the seating for 737-8 if using a cabin configuration used by low cost carrier Norwegian Air Shuttle for its 787-8 based long range network. The ERX would then seat 168 passengers versus 787-8 291 (Norwegian’s configuration gains seats by not including lie flat or steep recliner seats). In this comparison the 737 MAX 8 had 15% lower Direct Operating Cost, an ERX variant would be close to such figures.


The low slung 737 limits what Boeing can do to answer the A321LR move by Airbus. We concluded at the time that the most promising alternative for Boeing would be a higher gross weight variant of 737 MAX 8. This is now tested on airlines which has a need for a long range single aisle alternative.

While limited in its passenger capacity our modeling shows highly competitive economics for the seats flown by a Boeing 737-8ERX.

45 Comments on “Boeing showing 737-8ERX concept in response to A321LR

  1. Thanks for reporting!
    This “LEGO” principle applies to both single aisle family, there is no hard limit to why Airbus cannot combine the A321 wing with the A320 body. Would allow a ~85t A320. The additional body fuel tank in the fwd hold would still allow sufficient baggage space (assuming 150 Pax), and probably give the A320 a similar range (4000nm appears realistic). The question is: how many airlines ask for such “low volume long range” routes.

    • I’m not sure if a 85 tonne A320neoLR would really need the A321 wing. Compared to non-sharkleted A320s/A321s, the sharklets are providing significantly better take-off performance and rate-of-climb and higher optimum altitude.

      As for the “LEGO” principle, there’s no hard limit why Airbus couldn’t combine; 1), an A320neoLR wing with a 7 frame stretched A320 body (i.e. A322neoX); and 2), the A321neoLR wing with a 10 frame stretched A321 body 8 (i.e. A323neoX).

    • My airline found that when we tried to operate the 320 with an Aux tank to solve the transcon range problem the CG range became to narrow at high weights and consequently it didn’t work. We ended up stripping the Aux tanks out.

      Our transcon A321’s have two tanks and even at very high weights we haven’t had a problem. I would tend to think therefore that a higher weight A320 with Aux tanks would probably not work based on past experience.

  2. A clever move to boost the 738 into the MOM range-wise, at minimal costs and in shortest possible time. The result is a kind of 751 MAX. The biggest inconvenience of this clever contraption is the non-availability of containerised cargo. 4,000 nm is not tip-top for TATL but we are getting close. The real good news is RAMP-UP ! : 52+ units/month overnight ?

    • Afaics the doubled transition cost from NG to MAX ( in relation to the Airbus CEO to NEO transition effort ) carries over into this project. All the changes presented will be more expensive than what Airbus has to add to the A321NEO to deliver a A321LR.
      Nonetheless as presented an interesting offer.

    • Since when did the 737 carry containerised cargo ? I dont think it even carries ‘containerised’ baggage. Remember the lowlevel baggage hold and smaller doors .

      • @ dukeofurl : please read once more what I said in March :
        Quote/The biggest inconvenience of this clever contraption is the non-availability of containerised cargo/Unquote.
        Translate : regretfully, the 737 has no CLS – Cargo Loading System
        Do we agree ?

  3. Thanks Bjorn and Scott

    It’s a shrinked 737-9 !
    In the lego box there’s P8 Wingrakes ! are they better than split winglets ? Why not providing an interchangeable “wingtip”, one for domestic fleet one for long range fleet ?

    Bonne journee

  4. we are going the way of the baby airbuses that go from LCY to the states but without the stopover. Presumably BA would be very keen to get a couple if that route is working

    • Only the A318 is qualified for London City. Going transatlantic from London is possible with today’s A319. Two ACTs and highest MTOW option gives 4000nm still air range with 10t payload (around 100 passengers). The A318 needs a stop because he is MTOW-limited out of London City.

      • I was being facetious, apologies. Just reflecting on the ever reducing size of the aircraft plying the Atlantic.

      • Thats correct, the mtow is limited at London City by the short runway. Additionally BA have an aircrew time constraint as the AC sign on at Heathrow then travel across the city to fly out from LCY. This leads to a crew change at Shannon during the US customs pre clearance.

    • The LEGO box is (still) interesting to play. I wonder f the A321 LR wings, 35K PW1000 and wheel brakes would be an option. A London City BA A318/19 STOL 🙂

      In my opinion, as Schorsch mentions, how much of a need is there for 136 seats flights on the Atlantic. It is going to be 136 passengers that have to pay for the pilot, crew, aircraft, fuel, slot, gate, services, ATC instead of 164. That won’t help prices/margins. Prices are determined by the market/ competitors.

      The easiest, and for Boeing most threatening, LEGO box option is the A320 Plus. Optimized for a realistic 200 seats/ 4 crew, 2 rows longer then the 737-8. If Airbus starts proposing such an A320, Boeing will launch an NSA within months. And Airbus probably doesn’t want an NSA.

      • I never understood why the A320.5 has never been developed. Big wing for ER from the A321 and small wing from the A320 for short haul Ryanair stuff. Lego is great.

  5. The key restraint for all 737 derivatives is the MTOW offered by the most powerful engine that can fit under the low wing. That is the limit. How many airlines want to invest in a plane that is the final evolution of an old program rather than wait for a new 757 replacement? Boeing has brilliantly tweaked and tweaked, but aren’t we reaching the end of the game hear? What would the residual value be of such an “end of the line” plane?

    • Good questions. The answer to number one seems to be, “Quite a few.”
      I do believe that we are reaching the end of the game, especially when one considers that Boeing originally intended to end it a few years ago until forced into doing a 737 engine modernisation based upon the success of the Airbus NEO.
      The residual values of These aircraft is the big open question. I assume that there will always be someone who is willing to pay for one of these older frames, especially if the fuel prices do stay low.

    • Boeing will never admit they made a huge mistake by not just idling the 757 Program down 10 years ago. Granted it’s a low-volume “niche” market that the current 757 Series caters to…………but all planes that are used rigorously 15-20 years………need to replaced.

      When Boeing chooses the “quick” allure of Billions in Tax Charge-OFFs on the 747-8 Program………again…….Freight Companies will be furious (15-20 years time) that new VLA Freighters are no longer available.

      And of Course Boeing Management will never admit Bad Long-Term Business Focus.

      Every market they (Boeing) have abandoned (allegedly because the margins are to low,Cyclic of effect of aircraft purchases and lifespans). Embraer,Airbus,Japanese,Chinese will swoop-in and eventually Dominate. What, Boeing will be at the peak of 787 Production in 10 years Time.

      With plenty of Classic 777/787 still in Service and with 10+ years of Flight Cycles left in their Air-frames then ………….Boeing will be struggling to get by on 737s

  6. This Boeing new FrankenLiner is a kind of admission of the problem they are facing with their aged 737 platform.

    It is time that the great Boeing comes up with a new design for the next 30 years.

    • I really detest that Franken nonsense. It shows gross ignorance on the part of the sender. One of the very low moments in Airbus PR (and Boeing has it as well) . It seems people are Franken created as well with all that mixing up of genes and DNA and such.

      There is nothing wrong with using perfectly good components to make a desired aircraft (KC46 or whatever they called the 767KC)

      More than fair comment is what does doing that to the 737-8 get you?

      Seems like not much if anything.

      So, no question Boeing has screwed itself into a corner with the 737 (as much as I love it) and should have come out with an all new hull a generation back.

      • There is nothing wrong with using perfectly good components to make a desired aircraft (KC46 or whatever they called the 767KC)

        The Frankentanker? 🙂

      • Well, I always thought it was Northrop Grumman that dubbed the Boeing’s 767-tanker offering the “Frankentanker — or maybe not:

        During the competition last year, an anonymous cartoon surfaced calling Boeing’s 767 tanker a “frankentanker” because its parts were made in different places. Thus, Crowe dubbed the 777 tanker the “bride of frankentanker.”

        Funny stuff:

        • Well, as I may have said in previous iterations of the “frankentanker” foolishness, pieces being made in different places is hardly a new idea – check Airbus investment in Super Guppy type aircraft and chartering of ships to carry fuselages.

          Avionics is often upgraded to newer – note the 747-400 flight deck which used knowledge gained on the 767 (2-crew digital).

          And grafting the 767 flight deck onto the 757 fuselage (albeit Boeing had been preparing the notion for some time).

          Integration is the key, Boeing botched that on the 747-400 initially, Airbus botched it on the A380.

      • The A300 had a similar grafting of new onto old when they did the major update for the A300-600 series.
        It got the changed rear fuselage of the A310( plus a new design of flaps etc)

        We all know that the A330 is a new wing on the A300-600 fuselage

        • Essentially only the cross section carried over and the tail layout providing more “living space”.
          Airplanes are designed around the wingbox/center fuselage section. There is no commononality there.
          ( I’d be surprised if any large structure parts are shared between A330/A310 and A330/A340.)

          • Yes, but I agree with duke that the A330 is to the A300 as to what the 777X is to the 777 classic.

          • 737,727,757,707……..were all built on Modular Wing-Box……….and exact Fuselage-Cores………..Boeing just mixed and matched pieces for the later 737 and 757 Program……..from the 727/707 Programs. 757 was the cash-Cow for Boeing all the way into the mid-1990s…………….it returned a better profit than even ole 747 and the then recent 777.
            According to Joe Sutter, Profits on the 767 Program have never been Great; do to its complex engineering and still can’t be beat High Aspect Ration (aft-Loaded)Dihedral Wings
            A340,A300,A310 ,A330 Series,etc are/were built on the same formula as Boeing did with the Original 707 Program………..A340/A330 differ in (Sharing) reinforced-modified Wing-Box to handle a Larger-Longer Wing for 2/4 engines….and greater fuel capacity.

          • The wing box is exactly as it sounds like and can still be essentially the same from A300 to A330. Up gauging in a few places is straightforward.

            With the A350 XWB, when they were forced to go for a wider fuselage they still kept lower lobe the same as the A330 and only made the upper lobe slightly wider- and of course with new materials.

            Toyota made an art of reclading their old cars in new sheet metal to present them as all new. Camry is a case in point

          • Dukeofurl, you should do your research better before making such sweeping statements. There is not a single part let alone design principle carried over from A300 to A330/340 wings (the 310 wing was in-between and it was also different to 300). The A300 wing is a low aspect ratio wing with high speed aileron between flaps combined with outboard low speed aileron and classical mechanical-hydraulic controls. Flaps are multi-element with mechanical links, front has Krueger flap+slats. Wing is made with classical aluminium piece by piece technique. No wingtip device. The A330/340 wing is a high aspect ratio one with un-interrupted flap line, movables controlled with FBW and using 4 milled wing skins per side and very different single element flap on track technique, front is slat only, wing has winglet. They could not be more dissimilar, your comments re A330 and A350 fuselages are as fitting as well.

          • Bjorn is totally right on the A330 wing design:

            That is what is what I said too

            “We all know that the A330 is a new wing on the A300-600 fuselage”
            The A350XWB had to have a wider upper fuselage to get the bigger cabin but the lower lobe could remain the same width as the A330.
            The rear fuselage doesnt have the taper of the A330 allowing a constant width passenger cabin to the last row

    • Replacement for the 757/737………… a big pipe Dream right-now or anytime soon in the future.

      Even the Authors of this Journal Platform seem to forget an important Criteria………..for another clean-sheet plane. Greedy Trade Labor, Office/Floor Engineering labor Syndicates-Unions.

      If you were a Large Global Company would you want another Major expensive to negotiate labor-Contract for Decades? Grand Fathering-in guaranteed wages/benefits even if the New Program Fails to Live-up to Expectations?

      I might seem like I’m siding both fences (and so in an unbiased-manner)

      Ask yourself………would you intentionally begin a New Program that is destined to wreak havoc on future Profits and piss-off the folks on Wall Street?

  7. Are we talking about a frame that basically is similar to BBJ2(MAX)?

  8. I think this model could be attractive to European LCCs, in particular Norwegian and Ryanair, looking to expand into transatlantic routes. They could fly west in the afternoon, fly back overnight and fit in a short haul flight in the lucrative early morning slot. This last flight is gravy, even if the long haul configuration is looser than they would normally use for the short haul slot.

    • Yep … but these ERX thin route concept aircraft (we could name them 751 MAX ?) are also excellent MOM route-openers and/or frequency multipliers to Legacy carriers around the world, in abayance of a future true MOM solution-to-be ?

    • Luckily its still available, as the 757 and 767 were designed to have the same cockpit/ nose section

      • imu 777 and 767 share the basic structure of the nose section.
        757 and 767 share the cockpit layout and viewing angles
        from the inside. It’s not the same metal.

  9. For airlines needing the range to fly in and out of Hawaii and Iceland, it looks like a good option.

    • Finnair is also a potential user of 751X. Small company, narrow routes, mixed use with holiday- and scedule operations!

  10. If I remember well, there is also a 737-700 with -800 mtow, tanks etc. I believe ANA is the only taker.

  11. Hawaiian air already flies in and out of Hawaii, as does Alaska Airlines form Anchorage and Seattle.

    The max will have better range. Do you need to fly Hawaii to Denver or Salt Lake?

    At some point its time for the twin aisle, single can’t serve all segments at all ranges.

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