I'm a full-time employee at University X, located in an East-coast
city.  My family wants to move to a West-coast city, where my spouse
will have a job.  I'm planning to keep my job at University X and fly
back each week (several dozen times in the next year).  When I
"commute" back to University X by plane, can I deduct the cost of the
plane ticket as an unreimbursed employee expense required for my job? 
What do I need to do to document the deductibility of this
arrangement?

Hello and thank you for your question.

Commuting between University X and your family's west-coast home is
not deductible.  It's no different than the costs of a normal commute,
say between suburban home and city job-site.

"Commuting expenses.   You cannot deduct the costs of taking a bus,
trolley, subway, or taxi, or of driving a car between your home and
your main or regular place of work. These costs are personal commuting
expenses. You cannot deduct commuting expenses no matter how far your
home is from your regular place of work. You cannot deduct commuting
expenses even if you work during the commuting trip."
http://www.irs.gov/publications/p463/ch04.html

When Are Transportation Expenses Deducible?
http://www.smallbusinessnotes.com/fedgovernment/irs/images/11081l02.gif

Search terms used:
work commute site:irs.gov

Thanks for bringing us your question, although this may not be the
answer you'd hoped to get.

Richard-ga

Right from the IRS manual.

You do not say in which country you are. In the UK, expenses incurred
in travelling to and from the primary place of work are not allowable
against tax for employees.

Owain

I'm in the USA.  The general rule as I understand it in the USA is
that ordinary commuting expenses aren't automatically tax-deductible,
but that there are a number of exceptions.

In the US, I am fairly sure that there is no way you could deduct this
expense as you've explained it.  Your job is not requiring you to do
this travelling as part of your job.  You will doing this travelling
because you want to be with your family.  The only travel expenses you
could deduct for your job would be required by your employer (e.g. you
are a salesman and the company needs you to visit an account in
another state, but does not reimburse you for the hotel, etc)

As posed, I believe that you are out of luck. If you can figure out
all of the nuances of incorporating where the eastern University
engages your "company" for your services then your travel becomes a
business expense of the company. That isn't financial advice but I
believe that there are legal ways to reduce the cost of the travel but
you have to get creative.

On a personal note, I think that you are setting yourself up for a
whole lot of trouble that you do not see coming now. The cheap flights
are generally not the non-stops, plan on about 16-20 hours/week in
transit. Assuming that you have a 5 day a week job, you will need to
leave the west coast by around noon or 1PM to get to your east coast
home in time to get some rest and make it to work the next morning. On
the other end, unless you can leave early on "Friday", you can't get
home before 11PM if at all. You will constantley be suffering from jet
lag. If everything goes well, and it won't, you will be home about 36
hours each cycle and pretty much dead tired for all of it.

You and your spouse will become more independent of each other. Your
kids will not be able to depend on you and family events will pretty
much happen without you. Sure, for a while the will delay the birthday
party until you get home but it won't be forever.

I did something way less demanding than this for over a year; two
weeks on the west coast and two weeks on the east coast. Almost a year
after stopping, I still have not fully caught up.

If you do do it, here are some tips:

1. Take care of yourself. Get enough sleep and stay out of fast food places.
2. Talk to you family every day. Get a flat rate long distance plan
and a nationwide cell phone plan.
3. Only one person in the main checking account. 
4. Have a secondary source of funds in case you don't heed #3.
5. Bose noise cancelling headphones are worth every penny.
6. Get on a first name basis with the airline people at both ends.
7. Plan on being bored or a workaholic.