Metaphorically, it may be a slow or tedious trip, a military air mission posing little danger, or any circular route.
Milk runs are documented in the American Upper Midwest as early as 1917, where it was a train that made frequent stops to pick up farmers' milk cans for shipment to local dairies for processing and bottling.
[5] In the airline industry, a "milk run" is a multi-stop, regularly-scheduled passenger flight operated with a single aircraft.
Current examples include: An historical example of a transcontinental airline milk run in the U.S. in 1962 was National Airlines (1934-1980) flight 223 operated daily with a Lockheed L-188 Electra turboprop aircraft on a south and then westbound routing of Boston - New York City - Jacksonville, FL - Orlando - Tampa - New Orleans - Houston - Las Vegas - San Francisco.
[9][10][11] According to the March 2, 1962 National Airlines system timetable, flight 223 departed Boston at 7:30 am and then arrived in San Francisco at 8:42 pm on the same day with seven intermediate stops en route.