Question about Z class availability
 

I am looking to book a flight with expert mode enabled on united.com and have run into an issue. I have selected business/businessfirst for my cabin and the only fares that come up are C class seats. I look on the available cabins for both my departure and return flight at there is Z class availability, at least Z1 or higher, why would the website default to C class at a fare almost double Z class?

Welcome to FT! This is a common question around here for newcomers.. in order to purchase a specific booking code there not only has to be inventory shown in the bucket, but there also has to be a fare published for the city pairs you're trying to book, and your itinerary must meet all the rules for that fare.

There either may not be a Z fare published or for some reason your itin doesn't qualify..could be not enough advance purchase (many Z fares have a 30 or 50 day advance), no Sat night stay, or you don't meet the minimum stay requirements.

Sometimes there can be space in a bucket but no published fare that allows you to purchase it. I ran into this problem all the time when I used EF to search for Z fares then could not book them, and the EF team explained this to me.

As a next step, you can try calling and see if you find an agent willing to check or help you.

Also, I find the ITA Fare Matrix helpful in uncovering Z or P fares.

Since you've given us so few details to work with, a non-exhaustive list of possibilities:
1) No Z fare published for your market
2) Advance purchase requirement
3) Minimum stay requirement
4) Saturday night stay requirement
5) Combinability restrictions
6) Display glitch
7) Roundtrip requirement

Without getting into too much detail I had previously booked this reservation, ORD to MTY in Z with only a 4 day advance purchase. This was work related and customer made us cancel night before the flight. So I know that Z is available as I am looking to travel the same dates, Sun-Fri.
I understand advance purchase requirement but stating available fare of Z and previously purchasing this fare is somewhat confusing.
I will have to call to book this, just curious as it seems odd that I was able to book the same route, same flying days with little advance purchase a month ago and now that option is not available.

Fare rules change all the time.

There are currently no Z-Class Fares published on that route, so there is no point in calling:

http://Help.KVSTool.com/#Q1

[KVS Availability Tool 7.1.6/Diamond - ATP: Fares/FC/Current]

Make sure you've selected the "Lowest Available Fare" button from the menu titled "What's Your Fare Preference?" If you select either of the less restrictive options, you won't get Z fares.

You "know" without actually checking?

As KVS pointed out, there isn't one.

http://i1294.photobucket.com/albums/...ps55f6c3bd.png

This is what I am talking about, United's website showing Z availability and yet I am bumped to C. I have tried using lowest fare and picking Z class specifically and that won't work. I can try booking using Y or B fares, as there is availability.
My biggest issue was that I previously booked this flight, had to cancel and the fare is over double what I had already booked.

Umm, it's a 3.5 hour flight on a regional jet.

SO not worth booking Z or C.

As for showing Z availability, that's not how "expert mode" and airline fares work.

You are misunderstanding how fares and buckets work on United.
1). The Z bucket is available on this flight.
2). There are no Z fares published for this route right now.

Therefore, you cannot buy a Z fare. United does not want to sell it, so they will not. Purchasing a fare requires that a fare is published AND the bucket is available.

A Z fare used to be published on this route. Then it was pulled. This is why you could buy it before, but not now.