I recently traveled to D.C. for a research meeting (Monday to Wednesday).
The cost was borne by the research grant. The cost of departing Saturday
P.M. and returning Wednesday P.M. was $550 less than a Sunday P.M.
departure. The Hospital insisted on the extra travel day to reduce the
total cost and did allow the hotel and per diem charges. I have seen all
three of your first options exercised with the goal of minimizing the
total cost. The Hospital has viewed minimizing cost as adequate
justification.

Can't help you on option 4, I have not had a test case.

One other way to lessen the cost of last minute airline tickets is to buy
two. Purchase the first ticket from your city to the intended destination
with a return flight one week later. The second ticket is a round trip
beginning at the destination city (of the first ticket) to your city again
with a return scheduled one week later. Each of the return trip tickets
remains unused. We have found that in most cases, the cost of the two
"over-Saturday" flights is still quite a bit less than the single last
minute round-tripper. If your office schedules tickets regularly, you may
be able to coordinate the tickets so the unused return tickets is used by
another traveller.

Bruce W. Steinert, Ph.D.
Department of Urology
William Beaumont Hospital
3601 West Thirteen Mile Road        (810) 551-2572 (Voice)
Royal Oak, MI  48073-6769           (810) 551-8107 (FAX)