The higher the fare the higher up you would be on the upgrade list.

And in each fare category the higher-level elite status would get the upgrades first. So with an H fare, for example, the platinum elites would be ahead in the list before gold, and the gold before silver. And so on and so forth in each fare category. So by the time you get to O fare, as a Gold elite, there is only a small chance of being upgraded.

If you really want to fly FC, I think the best bet is CO's discounted FC ("A" fare basis). In this case, this would cost you about $1,346. With this ticket you are literally guaranteed an FC seat. My $$$ are based, btw, on EWR-LAS 10/6/06 & return on 10/8/06.

If you buy a full Y fare, you would spend about $1,146 and, although you would receive a space-available upgrade when you buy the ticket, there is a small chance of getting bumped back to coach (there are some interesting threads about this on FT).

After that, the less expensive the fare the less likely it is an upgrade will be available.

This is one of the few domestic destinations which CO flies using 757's which have larger FC cabins than the 737's it otherwise primarily flies on domestic routes out of EWR. The 757's have 24 seats in FC, whereas most of the 737's flown on this route only have 14 seats in FC.

So your chances of getting an upgrade are slightly greater just based on the notion of more FC inventory being available.

Finally, if you do fly on one of the 757's, please note the coach cabin is slightly more comfortable than on CO's 737's. The 757's have one additional inch of legroom in coach, and that makes a big difference (of course, you can always try to get a bulkhead or exit row seat).

If you really want to fly FC, I'd buy the A fare. Otherwise, I'd just buy the cheapest fare. If FC is not critically important, why not just save your money? I don't know about you, but with the $1,000 difference between the full Y fare and the O fare, there is a lot I could do with that money. And, if you do get the upgrade, then it will be not only a great perk but also an incredible value.

Bon voyage!