I am not an expert on this, but I'll give this a question a stab...

"Peter R." writes:
In watching a freezing rain/snow storm move from the midwest up to the
northeast US today, I again wonder how the airlines deal with freezing
rain. Are many flights canceled during a freezing rain storm or is it
business as usual?

"It depends". Freezing rain can have several effects:

1. icing up runways and taxiways. It takes time for airports to
clean off the ice. This can mess with commercial flights.

2. coating parked or taxiing planes with ice. The ice needs to be
removed, which takes time. This can gum up schedules.

3. getting ice on planes as they fly. Most commercial jets fly
really fast, which has two effects: first, it means that the planes
will fly through the freezing levels quickly (and up higher where it
is too cold for ice accumulation), so they don't pick up much ice.
Also, the wings and control surfaces get heated by the passing air,
and are warm enough that ice doesn't tend to stick to the plane. So
in many circumstances the jet can just fly through the freezing
conditions and not worry about it.

Does a deicing on the ground and anti-icing equipment on the aircraft
provide the protection needed to fly into or out of freezing rain
conditions for the airline aircraft?

In many cases, yes (it depends on how severe the icing conditions
are). The presence of icing conditions would make the pilots be much
more careful about watching out for ice, but otherwise everything is
routine.

Now, many of the people in this group (including me) fly GA planes,
which usually fly lower and slower than commercial jets. For these
planes icing is a much more serious problem, and so we can't fly in
the same weather as commercial jets.

Think of it this way -- your car has windshield wipers. In light or
moderate rain, they let you drive in the weather without any problem.
But in an absolute downpour they may not be able to keep up, and so
you are better off pulling over and waiting for the rain to pass...

Chris