Originally Posted by
Hartmann
You mean the 767 and 777? The 757 is very easy to identify as it is slender and long (the -300 is the longest single aisle aircraft in commercial service).
The 767 and 777 share common parts and the main way to distinguish the 767 and 777 is the gear and the tail cone. The tail cone on the 777 is squared while the 767 is a little more rounded. Sheer size is another great way to tell the two apart.
The 757 and 767 were developed together, and share a lot of parts, although obviously not fuselage. The 777 was developed about 12 years later.
In addition to the tailcone difference, on the ground, to differentiate the 777 from the 767, you can count the wheels. 2 rows of two per carriage=767, 3 rows of two=777.