Re the 757 program, there was a 757-100 proposal that was quite far along in the development stage, it sat about 150 passengers. The 757 was originally developed as a 727-200 replacment, and the 751 was the closest in capacity to the 72S. Launch customers for the 757, Eastern and British Airways, each wanted the extra seating capacity offered by the 757-200 and that was the aircraft that went into production first. The next big order for the 757 was by Delta, who also wanted the seating offered by the 752, and Boeing never went any further with the 751 due to lack of interest by the airlines. Its strange how similiar in concept the 751 was to the 738.
Re the 767 program, Boeing did do some studies on a 767-100, a slightly shortened version of the 762 but nothing really ever came of it - the 762 was always considered the baseline aircraft for this program. When the streched 767-300 became available a few years later, almost all interest in the 767 program focused on the larger 763 and any plans to further develop the 761 were halted.
Re the 777 program, there have been two seperate projects that carried the 777-100 name......first was a simple shrink of the 772 which was presented to the airlines as an alternative to the 764 which did go into production. Key customers DL
believed that the 771 was too much aircraft, with too much wing and too much weight for their needs (especially DL
which was looking for a aircraft to replace its L1011s on domestic services)....strange, if Boeing went with the 771 instead of the 764, they may have had a better product to compete with the A332, but that is another story. Later, Boeing proposed the 777-100LR as its ultra-longrange airliner, and it is rumored that AA
was very interested in this proposal, but other target customers demanded more capacity (similiar to the 772) and Boeing went on to develop the 777-200LR instead. Airlines were concerned that the per pax operating costs of the 771 with its shorter fuselage would be too high (think 747SP).....it seems that SQ
was much more in favor of the 772LR, now lets see if SQ
orders the type.