the.com/milk run

means A trip, flight, or task that's so routine, easy, and predictable it practically runs itself.

from Rooted in the literal dairyman's round — the daily, same-route, same-stops delivery of milk door to door, a job famous for having zero surprises. WWII airmen borrowed the phrase for the easiest, least dangerous bombing or supply missions, the ones with light resistance, as opposed to the terrifying runs over heavily defended targets. From there it spread into general use for any routine, low-drama trip or task — commercial aviation still uses it for a flight that makes many predictable stops along a fixed route.