747 armchair pilot but 300 hour realworld pilot would like to know genuine, real life reasons for using RTE 2 in the FMC.
Thanks kindly for coming down to my level for a few minutes!
no problem, in most cases you are spot on and level here with this.
when it comes to rte2 : at scheduled airline operations with repeating flights the route is mostly stored in the fmc database and not put in manually every time . there maybe several possible routings to destination and due to e.g jetstreams the ops may decide which routing is optimum and so filed in the flightplan and tells you what routing you should select in the fmc.
it has little in common with unknown runways at departure/ arrival since at departure you should get the expected runway with your departure clearance at startup, when at arrival the runway and type of approach is still unknown you should nevertheless have to brief the approach when you finally get the information what you expect- selecting a pre stored runway then in the fmc is a thing of seconds and not an issue.
best regards