Airline depature times are a lie....

In the past few weeks, I've noticed a trend at airports.
When the gate folks talk about the timing of flight that is leaving, they refer to the departure time and the "wheels up time".

I understand the difference. Obviously, the departure time is when the plane pushes away from the gate and the wheels up time is when it actually takes off.

What I don't understand is why difference between the two times can be so great. And not just when you get on the plane, it leaves the gate and then you find out you'll be sitting on the runway for one reason or another.

I'm talking about when (this actually occurred at the Dayton, OH airport earlier tonight) at 6 PM, they announce the incoming flight is delayed, so the outgoing flight will be delayed from 7 something to 8:05, but the wheels up time isn't until around 9:30.

Being in the business of transportation/supply chain, I might think it is great that they can forecast both the departure and the wheels up times even though they differ by a large amount.

One the other hand, it is terrible that they know these things and yet can't make the process more efficient.

By the way, departure, as defined by thefreedictionary.com:
1. The act of leaving.
2. A starting out, as on a trip or a new course of action.

The airline definition is more like, "the act of hurrying up to wait to leave"...

Perhaps "wheels up time" should be, "departure time plus a time that delayed your departure by more than you would like"...

On a positive note, my plane just arrived, so we might actually leave close to on time.