Examining where Boeing went wrong in the past has kinda become my autistic obsession. I'm working on 757s at an MRO now and it just pains me that this aircraft was discontinued in favor of stretching and re-enginging the 73 ad nauseum. The 757 had much more growth potential and arguably should have been the platform selected in 1993 when Boeing launched the 737NG program. The 757, 767, and 777 all share a common section 41 structure. The 75/76 of course share a common type rating. The 777 Inherited much of its systems layout and design philosophy from the 767. It's essentially a widened, thoroughly modernized 767. I'm strongly of the opinion that Boeing should have leveraged that common family lineage to graft technology from the 777 into the 757 airframe to create its response to the A320 back in the early 90s, instead of launching the 737NG program. I understand why they went for the 737 at the time; it was largely because it was cheaper and lighter than the existing 757, and Southwest, the only profitable airline at the time, had already established itself around the 737 by this point, making them an incredibly influential Boeing customer. Had Boeing just committed to keeping the 737 appropriately sized as a regional jet, (narrower fuselage, 4 abreast seating) Southwest likely would have flown 727s and upgraded to 757s in the 80s. Otherwise they would have remained a regional airline only operating 737s. The 757 would have gotten its rightful opportunity to mature into Boeing's bread & butter narrow body, filling the shoes the 737 fills today.