I just faced a situation where US Airways changed elite frequent flier standby rules after I had purchased my ticket. To make matters worse, reservation agents were not aware of the change in rules and twice assured me, the day before travel, that I could stand by for an earlier flight with no problems.

Unfortunately, there was a problem. A new, evermore arcane frequent flier standby rule had been instituted that blocked the computer from doing what I had been assured would be allowed; by the time supervisors figured out what was happening, my earlier flight had departed.

Needless to say, I was miffed. Not only had two reservation agents advised me, in error, about the now-defunct standby rules, but I was out early-morning taxi fare and about two hours of my morning scrambling to figure out what was happening.

Sometimes, it seems, airlines make their fare and frequent flier rules so difficult to understand that even their own agents — both on the telephone and at the airport — cannot figure out what rule is in effect, how to apply it and when. Worse yet, after dealing with the agents’ ignorance of their airline’s own rules, consumers are expected to pay an additional $35 for the pleasure of working with a human being.

Finally, I know that the Department of Transportation (DOT) has instituted a rule that forbids airlines from changing the price of airline tickets after tickets are purchased, but what about fare rules? Can they be changed willy-nilly at an airline’s whim?

Here’s a bullet-point outline of the situation as it developed:

• I called US Airways reservations on Saturday morning to explore the costs of changing my reservation to an earlier flight the next morning, the same date as my original ticket scheduled for 3 p.m. I was informed by the agent that since I was a Silver Preferred member of Dividend Miles, I could standby for the 8:55 a.m. flight at no charge if there was space available. She checked to see how many seats were available on the flight and told me that it “looked good.” She suggested I call back to reservations in the late afternoon to make sure availability had not changed.

• I called US Airways reservations again in the late afternoon and spoke with a delightful agent who checked availability on the 8:55 a.m. flight and informed me that the flight had opened up even more and that there were seats available in both First Class and Coach. She admonished me to get to the airport at least an hour early to go through the standby check-in.

• On Sunday morning, I arrived at Washington Reagan Airport at 7:55 a.m. ready to check in and get my standby seats. Unfortunately, the check-in area was in absolute chaos. The First Class/Dividend Preferred counter was unmanned and I was told to wait in the normal bag check line to find an agent. That wait took more than 30 minutes as US Airways personnel searched for an agent who could access the computers to deal with my standby request.

• When an agent was located, she informed me that US Airways had changed the standby rules earlier in the month. The new rule would not allow me to stand by for the earlier flight. It seems the new rule limits standby requests to flights within six hours of the confirmed reservation. My 8:55 a.m. flight was 5 minutes outside of that new rule restriction since my original reservation was for a 3 p.m. flight.

• I asked to speak with a supervisor who might be able to override the rule. I also called US Airways reservations. While waiting for the supervisor, the telephone agent basically said, “Whoops, we messed this one up; let me see what I can do.” Just as the supervisor arrived the telephone agent apologized that she could not do anything from her end. The supervisor would be the only one who could override the system.

The supervisor figured out what had happened and started to work through the system to give me a boarding pass. By this time, it was 8:40 a.m., with the flight scheduled to depart in 15 minutes. I suggested that the supervisor, before working through the system, check to make sure the plane was at the gate. He did so, and told me the Jetway had been pulled. We were too late.

Again, I received apologies and a shrug from the harried supervisor. I shrugged back and headed back home.

This story is full of would-ofs and should-ofs but it all boiled down to an airline changing the rules of the game months after the ticket was purchased. Worse, the rule was changed and kept secret, it seems.

I, as an elite frequent flier, had not received an email or any other notification about the rule change (at least I don’t remember any notice). Obviously, at least two members of the telephone reservations staff in Phoenix didn’t get the memo about the rule change. (It was on their advice that I planned to fly standby on the earlier flight.) And, it seemed the counter staff at Reagan National didn’t know about the rule until the computer blocked them from checking me in.

I am following up with DOT. We’ll see how far airlines can go in changing the rules after tickets are purchased. More follows.