Originally Posted by meh130

The Z2 are the former Gulf Air (and one Asiana) aircraft with the different door arrangement. There are 5 left if the fleet, a few were sold off for cargo conversion last year. The former Gulf Air aircraft are some of the oldest 767-300ERs in Delta's fleet, and my guess is they will continue to be retired as newer aircraft come into Delta's fleet.

The L and the T are identical except the T is for flights of more than 12 hours, so it has an crew rest area in the forward cargo hold. This is accessed through a stair at the front of the Y+ cabin, which takes up the space that reduces the Y+ cabin by three seats.

The Z1 was developed from the L for routes with less demand for business class seats.

Some have mentioned the PSUs not having air vents on the Z2. The only other physical difference is the earlier 767-300ERs delivered new to Delta had the Pratt & Whitney PW4000 engine. Delta switched to the General Electric CF6-80 for later 767-300ERs. The Z2s also are CF6-80 powered.