Hi all. i just had a question: What is "commuting" and what is "commuting clause?"
Also, what does it mean when someone is "flying 121"?
Thanks.

Pilots are a little different in their commuting from the typical office desk jockey because their ride to work can be on an airplane instead of a car.
I live in Colorado Springs but I am based at Chicago O'Hare. Simply put, all my trips typically start in ORD and end their as well. Every couple days I head to the airport, go through security, and ask the gate agent for the jumpseat. Then based several mitigating circumstances like seniority, airline flying on, and first-come-first-serve bases, I may get the jumpseat. If the plane isn't full then I get a seat in the back, sometimes first class too. If the flight is full, or almost full, and there are non-revs (non-paying passengers usually somehow associated with the airlines) that are trying to get somewhere or a flight attendant trying to get to work, I do the right thing and take the jumpseat so they can get on.
Then on the last day of a trip, I reverse the whole process and do it in the opposite direction.
Basically, it is a way of life. You can see an article I wrote about commuting here:
http://tinyurl.com/bokuofAs for a commuting clause, that depends on the airline you work for. SkyWest does not have a commuting clause per se, but if we are having trouble getting to work, crew support will usually, but not always, allow us to take vacation time instead of getting written-up for missing work. United and Delta have different policies so I can't really speak for them.
Part 121 are the regulations that outline the operating requirments domestic, flag, and supplemental airline operators, like Delta, American, etc. Go to the FAA website (faa.gov) for more information.