The last straw for Mendie La Moure of Keller, Texas, was missing the last of four standby flights on her way to prenuptial events for her nephew's wedding in Fort Collins.
Her original United Airlines flight had been canceled, and she begged the airline to get her onto another flight that would get her there on time.
It didn't happen, and La Moure became one of a surging number of travelers filing complaints against airlines.
As the summer's record-high airline traffic winds down, many travelers have endured flight delays, cancellations, rude airline employees, overheated airplane cabins, lost baggage and hours of frustration at the airport.
Denver International Airport has been reporting record passenger traffic for the past 14 months. In June, nearly 4.4 million travelers used DIA, up 7.9 percent from a year ago. DIA passenger traffic for the first six months of the year was up 11.1 percent from the same period in 2005.
Planes have been fuller than ever. United Airlines reported a record July "load factor," which measures how full planes are, with flights 87.7 percent full on average in the month. Frontier Airlines planes were 85.2 percent full on average in July, up from 81.9 percent a year earlier.
With more crowded planes, "there's more likely to be service hiccups," said Air Travelers Association president David Stempler.
The number of air travel complaints filed with the U.S. Department of Transportation for June, the most-recent data released, increased 18 percent to 758, from 640 in June 2005. The airline with the lowest rate of complaints was Southwest, while the highest was Mesa.
The numbers represent only a fraction of dissatisfied customers, because most people do not file complaints with the DOT.
Flight problems, including cancellations, delays and missed connections, were the most common complaints, followed by baggage. Third was customer service, including rude or unhelpful employees, inadequate cabin service and treatment of delayed passengers.
No airline is exempt from mistakes. "I always tell people, if you fly long enough, you'll have a problem," said Doug Skelton, director of customer relations at Frontier Airlines.
Stempler expects to see an uptick in baggage-handling problems since the mid-August ban on liquids in carry-ons, including longer lines to check bags, and mishandled bags.
Bad weather also increases the risk for trouble.
Traveler Meryl Kahn ran into problems with a flight from Boston to Columbia, S.C., in July during floods in Washington.
After her flight was canceled, she says she got conflicting information from United Airlines on how to get rebooked on a different flight and where to pick up baggage.
"We couldn't trust anything we were being told," Kahn said. The trip from Boston to Columbia ended up taking three days, including two nights spent in the Washington area.
Stempler said he hears passengers all the time say, "'I swear I'll never use this airline again.' But if it's still the cheapest and the most convenient time, people tend to go back to those carriers." Most travelers will not choose to inconvenience themselves because they had a past bad experience, he said.
United Airlines has been studying how to improve the experience for premium customers through a pilot program in San Francisco, including separate boarding lanes for premium customers.
"Getting this work right and earning our fair share of these travelers' business can mean hundreds of millions of dollars in additional profit for United," the company told its employees last week.
Frontier spokesman Joe Hodas said, "It's the way (customers) are treated by our employees when they fly us that brings them back to our airline, so it is absolutely essential to the bottom line."
Working in airline customer service can be challenging. Passengers can be tense about flying, and many factors are beyond the airline's control, such as security lines, weather and other airlines' cancellations, Hodas said.
Complaints about U.S. airlines have jumped more than 29 percent this year, according to the Department of Transportation, with big increases in canceled flights and baggage problems.
United was to open its check-in area at 2 a.m. today, about two hours earlier than usual. It's also putting plans in place to fly workers into Denver from other hubs.
Tight schedules, full planes set stage for delays. Labor tension and an aging air-traffic-control system also contribute to an ominous situation.
Delays in the nation's aviation system intensified in October, causing the airline industry's on-time arrival record to fall from September's level, while still remaining ahead of last year.