Another idea might be AirTran's "X-fares"

http://www.airtran.com/specials/xfares/index.jsp

Now, they fly to Flint (FNT) which is 50 miles from Ann Arbor, so transportation to/from may not be ideal, but they do have dependable service with these stand-by fares.

And don't forget to check fares from Toledo (TOL) which is about the same distance from Ann Arbor as Detroit (DTW) is, though of the three, only DTW will offer a non-stop flight.

(TOL is served by ATA which has driven fares down out of there).

Many moons ago when I was in college, there were offers for students combining Credit-card membership with student fares. Citibank had one with AA, Amex had one with NW, then CO (or was it the other way around?)

These offered zone fares to students. I'm not sure if they still exist. Can't find'em presently.

Something your student may want to check out is:
http://www.collegeplus.com/
aimed at United Airlines travel.