I will take a stab at the first question. US airlines do not base airplanes tail numbers at each hub. The airplanes move about the network. Ere may be us fleets based out of certain airports such as UA
having domestic ETOPS 757s based out of LAX
and business elite 757s out of EWR
, but each sub fleet usually moves around the entire network operated by that sub fleet. AA
in the past isolated 737s to MIA
and MD80s to ORD
, but event within that operation the airplanes all routed throughout the network. UA
has moved the entire 747 fleet to SFO
, but each airplane tail number flies every route, the same way they used to when they had 2-3 routes out of ORD
There is a difference between closed routes ( isolating specific planes to a specific set of routes) and managing a sub fleet. UA
does not used closed routings, but does isolate entire subfleets.
Closed routing airplanes is bad for the maintenance. It is harder to get airplanes to airports to do maintenance since most airlines do A Checks for an individual fleet at only a few airports. Also it makes the hours and cycles not match up which again is bad for scheduling maintenance. For example the 16 ETOPS PMUA
airplanes fly to Hawaii and tend to have longer segments. Maintenance times have to be adjusted for these planes because the hours /cycle ratio does not match the rest if the fleet.
The one exception at UA
has been with the IPTE 777s and non IPTE 777s as they have been working through the reconfiguration. For the last few months, they had the 3 old config 777s in a closed SFO HNL NRT SEA NRT HNL SFO
routing. This was to offer a more consistent product.
If you have never designed an airplane part before, let the real designers do the work!