As airlines try to automate more and more of their business, one increasing fact of life for travelers is the automatic rebooking program.

Instead of calling or lining up or even going online to have an agent rebook a flight where there has been some kind of travel disruption, travelers now get messages about possible or probable missed connections, along with a new alternate flight.

The rebooking systems are good, but by no means perfect.

I’ve received the messages when I’ve actually missed a connection or had a canceled flight, but other times I’ve been able to make my connection because the conning flight was also delayed. These programs aren’t sophisticated enough to consider if a second flight is on time. You have to do this yourself when you land.

Airlines laud these programs as a time-saver and improvement for clients. Of course, what they are is a money-saver; in theory it means less humans involved in the rebooking process.

My clients on Saturday had just over an hour connection in Denver to Salt Lake City for a ski trip. Unfortunately, while it was the third day of spring, it was also the day of a major Colorado snowstorm.

Their plane from Dulles was delayed by the snow, but their connection turned out to be the only flight to Salt Lake City that was on time all day. While it was a family of five (one of whom was a top level elite United flier), they missed their connection by about 10 minutes.

United sent them an automatic rebooking message for the next available flight, which happened to be about 28 hours later. An agent meeting the flight said there was nothing else available.

Had they accepted United’s offer, it would have meant finding a couple of hotel rooms and losing a day of an expensive prepaid condo rental (with no guarantee of any compensation).

When they contacted me, I waitlisted other United flights, and eventually found seats on Frontier Airlines late that night, which would mean at least 8 hours in Denver, but would be better than losing an entire day. However, we had no sense of whether or not United would allow the change.

Then, while checking the standby list on United.com, all of a sudden a sold-out flight about two hours later showed “available.” I tried to request seats, and actually got five of them.

At the United Club, an agent initially expressed skepticism that they would have reservations on the flight, since it was full, but when confronted with a confirmation number, eventually issued them boarding passes.

(We still don’t know exactly what happened. It’s possible that some passengers who were at the airport earlier got my clients’ seats as standbys on the earlier flight, and that seats very briefly went into availability. None of the individual waitlists I had set up on the flight I ended up booking ever did clear either.)

The travelers were worried that the flight was now very overbooked so got to the gate early, but curiously enough, not only was there no problem with their seats, my client texted me that he counted five MORE empty seats on the plane.

Those empty seats may well have been the result of others whose late arriving flights meant missed connections, but whatever the reason, this almost certainly means that other passengers who meekly accepted the rebooking solution offered by United spent the night in Denver unnecessarily.

Now, with or without a travel agent or another way to rebook flights, there isn’t a guarantee that there will be a better option than an automatic program.

But the programs don’t waitlist, they don’t look for other airline options and they don’t keep checking back to look for cancellations. In addition, rebooking programs don’t check alternative nearby airports — say, JFK for Newark or Washington National compared to Dulles.

Moreover, in my experience, passengers who question the options are often flatly told that they have the best alternative flight and are discouraged from standing by or waitlisting other options.

It’s not just a customer service issue. In the case of my clients, seats ended up empty while many passengers had to overnight in Denver. Even if United didn’t pay for their hotel and meals, having the plane full would have meant five more seats to sell the next day.

Airport operations are an inexact science and I have some sympathy for airlines trying to do the best they can with delays and cancellations. No doubt the machines do speed up the process when the next flight is both relatively soon and available.

But when faced with a machine-generated alternative that’s less than ideal, my advice to travelers is get a human on your side.