This question is not intended to create an A vs B debate (hopefully we are beyond that around here), but rather to try and understand the technical features of the B73NG that limit the NEO option in the future. While I fly and know stuff about a single engine light GA aircraft, I have no technical knowledge of the NG, nor any other aircraft in that class, so apologies for any implied lack of knowledge in this question.My understanding of the restrictions on NEO development in the NG is one of ground clearance of the wing. I assume that this is directly related to the main gear strut length, which in turn is limited to displacement from the fuselage center of the gear (to let both main gear retract toward each other without hitting each other), and the fact that the gear is appended to the fuselage and not the wing itself. (On that last point I have no direct knowledge- however I did have the opportunity to visit a presidential library last week where a retired Air Force One- a modified B707- is displayed- and while I don’t know how the landing gear attachment has changed since the 707 era it seems that the mechanics that the landing gear main strut is attached to was clearly appended to the fuselage and not the wing- this was observed looking up at the landing gear bay from underneath the AF1 aircraft).Having just spent a number of hours awaiting a B738 flight with Alaska Airlines at KPDX, who operate a large NG fleet, I also noted that the extended gear placement is offset from the fuselage by the length of the gear strut- about 3 to 4 feet, or so it seemed from a distance- and there was a considerable distance from the extended main gear to the engine- the gear was located much closer to the fuselage than the engine. This would make sense to avoid physical stresses on the gear strut mounting to the fuselage, I would assume, that would result from moving the gear further out towards the engine. And I must add that I have not had the opportunity to look at the mechanics securing the gear strut assembly on the NG, although I assume it is looked at regularly by the flight crews.As I’m sure we all know, the Airbus A320 class of aircraft is undergoing an NEO design, resulting in a larger N1 fan (with better fuel economics). We know that the A320 fuselage is wider by about a foot (if I’m correct), which would give each gear strut an additional 6 inches of extension if mounted in the same manner as I assume the NG gear is mounted. But looking at the gear from behind the aircraft, it appears to be considerably extended out from the fuselage in comparison with the NG, actually closer the engine than the fuselage. And therefore the gear strut assembly appears to be considerably longer than that on the NG.I know that this is a bit off topic (but I assume that wood pigeons are also in that category ). Having looked at these aircraft from the gate area environment last week (I also flew a leg with Frontier, hence the references to the Airbus aircraft), I’m now curious how all this works. Thanks, Bruce.

I think there's other considerations that will probably lead Boeing into developing an all new plane instead of yet another 737 remodel.1. The design is just old - 737s have been around since the 60s. Even the NG design is going on 20 years now.2. A new airplane would allow them to make something that has a ton in common with the 787 - parts, cockpit etc. This will save airlines money because it'll effectively be the same fleet as far as mx and training costs. I don't know how many here have actually sat in a 737 cockpit, but it's really small and not that great for pilot comfort - I'm sure they could do better with a new plane on that front.3. It would also allow them to try some new and innovative things with the fuselage - I've read rumors that they're seriously considering doing a plane that's slightly larger than a normal narrow-body that would have 2-2-2 seating. I think this would be great, passengers hate middle seats and it would give the new plane (797 presumably) something to really differentiate it from the 320neo.4. A lot of 757s are nearing retirement and the 737NG fleet never really totally covered that segment - the 900 doesn't carry quite as many people and doesn't quite have the same range, so I'd bet on this new thing being the true successor to the 757 the same way the 787 is to the 767.

Thanks Ryan, yes- that makes a lot of sense, given the facts you describe, to start anew with the next "baby Boeing".Thanks, Bruce.

http://www.flightglobal.com/blogs/flightblogger/2011/02/boeing-ceo-jim-mcnerney-were-g.html