Originally Posted by mahasamatman
In general, you cannot book specific fare classes on united.com - it will give you the cheapest fare that matches your search parameters (based on class of service, upgrade eligibility, and promo code). If there is a Z fare offered on the route you want, and you search for Business Class fares, you will get the Z fare. If the flight shows Z fare availability and you don't get a Z fare, it means that there isn't a Z fare offered for that route (or the C or D fare is cheaper - unlikely).
Not quite. There could be a Z fare available in the market you are looking in, but you might not meet all the fare rules.
For example, intl Z fares are usually quite restrictive and typically require an advance purchase anywhere from 21 to 60 days. This is the most common problem people have in not finding Z fares.
What are your dates and city pairs? I can check to see if a Z fare is even offered, and if so, why you are not being offered it on united.com.
Oh, and welcome to FT,
beanex! ^