<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by mauld:
????? Not sure what you're talking about, I fly CO very regularly on short weekend/long weekend (Thur/Fri-Mon) trips both in the US & overseas (Europe/Asia), always get cheap, yet upgradeable fares and have never seen anything saying I needed to stay 6 days. Perhaps this requirement is only on certain airlines, UA, AA, etc???</font>
IME, it's mainy Asia fares where we're finding the longer stay requirements- didn't people complain when UA introduced one on SIN runs? For a CO example, the fares CO had for the reintroduction of EWR-HKG originally had a minimum stay (the current one specifies none):
Continental Airlines to Resume Nonstop New York - Hong Kong Service
http://www.flyertalk.com/forum/Forum20/HTML/008260.html
My guess is that it's often another thing (as with saturday-night stays) to discourage business travelers from using cheap tickets. If you have a day or two of meetings somewhere, a 6-day min.stay fare is of little use to you. Discouraging mileage runners is lower down the list of importance, IMHO.
P.S. I thought "cheap, upgradeable fares" was an oxymoron on CO!