I worked for USPS for a few years at various positions..packages are never intentionally sent "out of the way" just to fill a trailer...often trailers may be half empty and sealed with US mail...and even airmail is put on a trailer and delivered to the nearest "sort" facility aka Bulk Mail Center (BMC) now called Network Distribution Centers (NDC)....USPS scans the zip code of EVERY package at the 21 NDC sort facilities in the US that every package must go through twice, the departure city nearest NDC and the arrival city nearest NDC..USPS is all automated and that zip code entered and scanned at the NDC and redirects the package via electronic automated conveyors belts to the exact correct trailer headed to/near that zip code, where it is then sorted again by the NDC and then trailered to your local post office and delivered to your door..at these NDC sort facilities, these conveyor belts are electronic and extend directly inside to the nose of each trailer, where mail handlers simply just build walls of packages to prevent shifting of loads, there is nothing else they do..so there is no way a package can be intentionally shipped to the wrong place unless an incorrect zip code is entered by a scanner which scans 1 package per second, and is being watched by at least 3 different people and rated for quality of performance.....most all USPS mistakes are made at your local post office clerks and daily mailman/carrier who will let a package sit for days and not sort it for shipment to the NDC if going outbound, or let sit all the inbound packages and not sort those to the various routes within that town..,,,there never is a required date of delivery unless U pay extra and upgrade to a specific type delivery , and same goes with any packages or letters requiring a signature or receipt requested..
San Fran and New York are the 2 busiest NDC's because of overseas mail and they being ports of US entry, and US customs inspections and waits..
JR, your mail lady doesn't know the system, and yes every package is scanned at a NDC...and I have never signed for any package fro USPS from Fasttech unless I requested that specific type shipping and paid more for it..