[reaperducer]

This is absolutely true.

I can't count the number of times I've been on a flight where the captain said something like, "Well, we left a little late, but we'll make it up on the way there, and expect to arrive on time."

I've had international flights leave an hour late and still arrive on time.

[SEJeff]

By default, flights are optimized for cost. Pilots can fly faster and burn more fuel to arrive at a destination (depending on reserve and bingo fuel of course) sooner. The goal is to use the minimum amount of fuel to get somewhere however and incur the most profit per passenger as a result. When you look at it, life really is an engineering problem.

[reaperducer]

By default, flights are optimized for cost.

Decades ago, before all of the routes and scheduling got to be more of a mesh than an ideal hub-and-spoke, this was an absolute. But now, being late can cost far more money than what would be spent in fuel.

Now, very often the airlines would rather burn some fuel and keep a plane on time than delay or cancel a dozen connecting flights at the destination.

[SEJeff]

I was noting the fact that they are able to change the speed of a plane to optimize for the specific key performance indicator they deem the most necessary at the time.

I used to work in IT for delta a touch over a decade ago as a systems engineer.

[fomine3]

Optimize for fuel cost means that planes usually don't fly at maximum speed. It also provides margin to avoid being late by speed up.

[SEJeff]

Precisely!