Ground Stops and Ground Delay Programs

I'm looking for some help understanding Ground Stops and Ground Delay
Programs...

In order to reduce arrival rates airports have the following 'tools' to
use...

1. ask a flight in the air to 'Slow Down'
2. ask a flight in the air to 'Hold' over the airport
3. issue a 'Ground Stop'
4. issue a 'Ground Delay Program'
5. other

My understanding is that Ground Stops and Ground Delay Programs only
affect flights that have *not* left the departure runway yet. So, once
in the air a flight cannot be affected by the Ground Stop or Ground
Delay Program tools, but can be affected by the Slow Down or Hold
tools.

Is this correct? If I was, for example, creating a report of all
flights affected by a particular Ground Stop or Ground Delay Program,
can I simply ignore the flights that departed *before* the Ground Stop
or Ground Delay Program was issued?

Thanks.

bobfuller30004hotmail.com wrote in message
My understanding is that Ground Stops and Ground Delay Programs only
affect flights that have *not* left the departure runway yet. So, once
in the air a flight cannot be affected by the Ground Stop or Ground
Delay Program tools, but can be affected by the Slow Down or Hold
tools.

That is correct.

If I was, for example, creating a report of all
flights affected by a particular Ground Stop or Ground Delay Program,
can I simply ignore the flights that departed *before* the Ground Stop
or Ground Delay Program was issued?

Depends on the report.

D.