Thanks everyone for your feedback and kind advice. The reason that I think UA/AA might have deeper discount coach fare is that UA is currently running a special to Asia for outbound travel by Dec 7th or Dec 13th (depends on your destination). I was just wondering what they'd do for the Xmas holiday considering less business travel in this period.

As to the availability of Z-fares, the deep discount business fare has a specific season requirement, as "PERMITTED 19NOV 07 THROUGH 25NOV 07 OR 28NOV 07 THROUGH 30NOV 07 OR 05DEC 07 THROUGH 07DEC 07 OR 18DEC 07 THROUGH 31DEC 07 ON THE OUTBOUND TRANSPACIFIC SECTOR". Of course, the 21-day advance booking applies. Therefore, I think I can hold out for several more days to book on UA if needed. I also did a search on NW and they appear to have comparable Z-fares for certain days that fit my schedule, which could be another option. The NW website appears less informative than UA, I must add.

With regard to trade offs between comfort and cost, I'm not tall and have taken transpacific flights in coach - it does not "kill" me but I might need work from home the day after (doable given the anticipated work flow). When I was a poor student, I typically paid ~$1000 for transpacific round trips; right now I may not mind a difference of $2000 ($3600 w/Z-fare) but would be kicking myself should the coach fare lowers to ~$1000 (instead of ~$1600) in the coming weeks.

Again, many thanks to all.

delta