Of all the frequent flier awards, for many travelers upgrades are the most prized, especially for international travel. With good reason — ten hours or more in coach is generally something to be endured. The same time in business class can be a mini-vacation.

Years ago, when clients waitlisted upgrades, there was a high probability they would clear. But a combination of better yield management and a system that favors high status travelers has reduced that probability dramatically.

For international flights, discount business class fares, a relatively new innovation, also can greatly reduce the available seats.

In addition, many airlines put no upgrade seats on a flight at all when it’s first available for sale. While they may add the seats later, it won’t help people already on the waitlist. Especially if they get their miles from credit cards instead of actually flying.

Here’s an example from a recent personal trip. I was traveling with my husband and son on a trip east with a connection in Dulles. We were all flying with return flights at different times; so, we were on separate records.

My husband is an Executive Premier — 50,000 miles a year — with United. We booked the trip, for July 1, in April. I waitlisted him for an upgrade using miles at that time. The plane was an Airbus, only 12 first class seat, but figured it was worth a shot.

Then in May, I added my son, who is a regular Premier — 25,000 miles a year — to the waitlist with his miles.

For myself, a 1k — 100,000 miles a year — flier, I did nothing special; United offers free standby upgrades in theory to all passengers who are premier and above.

So with the standby upgrades, I was added to the waitlist 100 hours in advance. The flight still showed sold out for upgrades, with five seats left.

On the night before departure, my seat cleared for a first class seat. Not only did my husband and son’s waitlist never clear, but also they weren’t even at the top of the waitlist at the airport despite their early addition to the list.

I certainly understand United’s desire to reward their most frequent travelers, and other carriers have similar policies. A higher status flier added to the waitlist at the last minute will trump a lower status flier.

With so few upgrade seats available, some of the highest status fliers are still ending up in coach, while lower status travelers on popular routes have almost no chance.

In fact, I had a Premier Executive flier who asked me to waitlist an upgrade eight months in advance on a full coach ticket this spring from San Francisco to Hong Kong. The night before, she was still waitlisted, with 12 seats left in business.

However, as a helpful United reservationist told me, at least 30 people were in front of her on the list. (In this case, the client was so frustrated she canceled and had me buy a business class ticket on another airline.)

I completely understand airlines’ intent to make money, and I don’t have a problem with them prioritizing their top travelers. The only issue I have a problem with is the heavy marketing of mileage programs, especially mileage credit cards, when the chances of actually using the miles is so small.

What I’ve started telling clients who aren’t frequent travelers, if a business class seat is a “necessity,” it’s worth considering an extra connection, or two, to try to find confirmable space. Alternatively, after figuring the miles plus co-pays, it might even be worth considering a paid discount business class ticket.

Otherwise, while it’s certainly not the end of the world, plan on sitting in the back of the plane.