The schedule is made by UA, the consumer accepts it. What UA factors into building that schedule is a combination of economic (connections/competitive) and operational (driven by stats) things. If UA builds insurance time for operational variables into the schedule and you find something on another carrier that gets u there for same price faster, take it. Only on FT is having insurance built into a product you already accepted considered a bad thing. Amazing!

Pretty much most manufacturers build tolerances into their product specs for variability. It's an assembly line, not a Rolls Royce. Economies of scale.