CHARLOTTE, N.C. ( TheStreet) -- Two weeks ago, flying from New York to Charlotte, I arrived at LaGuardia Airport early to catch the 3:40 p.m. US Airways' ( LCC) flight home. I was early enough that when I arrived at the gate, the 2:50 p.m. flight to Charlotte was still boarding. I asked the agent if I could take the earlier flight. He said, "Yes, lots of seats." But then he said he would have to charge me $75 to change. Not being a person who makes $75 an hour, I decided to wait the extra 50 minutes. My 3:40 flight left a few minutes late and arrived on-time in Charlotte. Like many people familiar with the airline business, I generally think positively about the industry's new fee-for-service model. I can argue that charging to check baggage is morally virtuous, because passenger's tendency to pack far more stuff than they need wastes fuel. I even think charging for beverages makes sense. Nearly every business in the world charges for beverages, except for the one that has to buy extra jet fuel in order to cart the beverages around until someone decides to drink one, free of charge. But charging a change fee to fly standby when a passenger is already at the gate seems not only avaricious but also disadvantageous for the airline. The charge could easily mean that a plane departs with an empty seat, which immediately becomes worthless. It also denies the airline the flexibility that comes with an empty seat on the next flight. Possibly that seat can be sold. Possibly it can accommodate a passenger who missed a connection. Possibly bad weather or congestion or a mechanical failure will delay that flight, pushing all the passengers onto future flights, creating unforeseen complexities and expenses for the airline. US Airways, United ( UAL) and American ( AAMRQ.PK) all charge $75 to change at the gate. All three waive the fee for premium level fliers and, of course, for passengers with unrestricted fares. Also, American spokesman Kent Powell said the carrier "empowers our personnel to make decisions which consider our overall operation and various other factors (such as) when there are operational issues or service disruptions."