The pilot's announcement had the ring of truth. The US Airways flight sitting on the tarmac in Washington, D.C., would be delayed because of "Y2K testing."

But on May 23, 1999, Jane Garvey, the federal government's top airline regulator, happened to be sitting in the coach section of the plane, and she hadn't heard a word about Y2K testing.

Garvey, head of the Federal Aviation Administration, dialed her office on a seat-back phone and confirmed there was no testing that day anywhere.

Minutes later, Garvey's call trickled down to airport officials, and the plane scooted to the runway for takeoff.

Garvey never received a clear explanation, aides say; the airline still has no answers. But she can now say she was denied the single commodity travelers are demanding more than ever: the truth.

Often accidentally, but sometimes deliberately, airlines give customers inaccurate, incomplete or inconsistent information. It begins before they ever buy a ticket -- with unevenly defined "on-time arrival" formulas that muddy performance comparisons -- and persists after they return home, with different airlines setting different times to start the clock for the industry's commitment to return lost luggage within 24 hours.

In between, gate agents boldly tell stranded coach passengers no hotel rooms are available during bad weather, when in fact hundreds are earmarked for those who have paid premium ticket prices or complain enough.

Only now that delays and cancellations have grown dramatically are many travelers beginning to resent the caste system that dispenses these perks.

But when things go wrong, all classes share a common feeling: frustration at not being told the truth.

The U.S. Department of Transportation inspector general's office has a long list of examples that confirm travelers' suspicions that they are often misled:

Airlines routinely blame delays and cancellations on air traffic controllers, when the real cause is bad weather, mechanical problems or crew shortages.

Departure screens frequently list flights as on time when, moments before a scheduled takeoff, there is no plane at the gate.

In some cases, airlines know hours in advance that a flight will be delayed but don't tell passengers until they are on the taxiway.

Airline officials maintain the misrepresentations are not deliberate. They blame their old technology for leaving agents misinformed and an overburdened air traffic control system that tangles flight schedules faster than they can explain them to the public.

To find the weak link in the chain of air travel information -- where hasty excuses grow and credibility withers -- watch Denver-based United Airlines customer service agent Carlos Ojeda.

On Sept. 11, a stormy day that paralyzed O'Hare International Airport, Ojeda stood face-to-face with passengers from the longest-delayed departure of the day. His United computer system could provide only a simple message: "airport conditions" had delayed an inbound plane from O'Hare that was slated to become an outbound flight from Denver.

Ojeda knew the plane was in Kansas City but did not know if it would arrive in time for the outbound flight.

Another plane might be swapped, but only the "zone control" workers in an unseen control center would know. Until they told him, passengers lined up and his only answer could be: "I don't know."

"That's the point where it all falls apart," said David Stempler, president of the Air Travelers Association. "When the information does not get to the people on the ground, they either say things that are no longer true, or things that they believe to be true. And often they're not."

Frequent travelers like Michael Faber are more willing to bear inconvenience than deception.

In April, the Warren, Ohio, resident says, a Continental Airlines gate agent told him his Cleveland-to-Nashville flight was canceled for mechanical reasons. But the mechanical problems were on another plane. Faber actually watched the plane he was supposed to be on leave with different passengers bound for St. Louis.

Continental had taken Faber's plane, which was functioning perfectly but was underbooked, and used it to accommodate the St. Louis passengers.

In hindsight, the gate agent should have told Faber which plane suffered problems, said Continental spokeswoman Julie Gardner.

"We believe our procedures for communicating are highly effective, but miscommunication can occasionally occur," Gardner said. "Unfortunately, this is what happened in this case."

Faber, who filed an official complaint with the U.S. Department of Transportation, is unimpressed with the explanation. "The thing I kept telling them was, 'Just be upfront and tell people what happened,'" he said.

Even as complaints about delays and cancellations have surged -- the Department of Transportation recorded 72 percent more complaints in the first six months of this year than the same period in 1999 -- resources for enforcing federal consumer protection laws regarding the airlines have been halved over the last 15 years.

The ranks of attorneys in the Transportation Department charged with enforcement have dwindled from 40 to 17 since 1985.

The cancellation or delay of one flight affects all its passengers -- but not equally.

When a problem due to mechanical troubles, crew shortages or some other fault of the airline occurs, most carriers will compensate all customers, coach to first-class, with free hotel rooms, transportation and meals.

But when a plane is delayed or canceled because of weather, airlines do more for their highest-paying customers. The dominant airlines at O'Hare -- United and American Airlines -- together reserve 250 hotel rooms a night in the Chicago area, dispensing most of them to premium passengers, while those with economy-class tickets bed down on benches and baggage carousels.

When delays foul certain KLM flights from O'Hare, business-class travelers are ushered to a nearby lounge and offered first choice of alternative connections. Coach customers queue up at desks back in the terminal.

Such consideration for those paying top dollar date to the early days of commercial travel. But the gap between the classes has widened over the last decade, industry analysts say, because airlines rely increasingly on business travelers, who are willing to shell out full fares.

United has announced its coach sections will now include several rows with up to an extra 6 inches of legroom, earmarked for the most frequent fliers or those willing to pay more. But the airline may have gone too far in distinguishing among classes of passengers, said Evergreen, Colo.-based aviation consultant Michael Boyd.

"Now you have Economy Plus and what I would call 'Economy Pig,'" Boyd said. "With first class, people expect that, but now they are clearly denying people the room to stretch out their legs just because they didn't pay enough."