Friends, refer Entry# 28909, I have taken a lot of efforts to explain PQ, its uasge, PQWL. I have done this explicitly for you guys. This will answer as to why end to end passengers in GNWL, why intermediate in PQ etc etc. All that you want to know abt PQ, with 2 different examples.
.
Note that this has costed me more than 1 hour to type.