Tens of thousands of airline passengers were stranded yesterday as American Airlines, the world's biggest carrier, was forced to conduct emergency inspections on MD-80 aircraft.
The planes are used on its short and medium-haul routes.
US authorities allow considerable discretion to airlines to inspect and fix problems with planes. But audits by the Federal Aviation Administration uncovered numerous examples of work that was not carried out properly.
Maintenance by US airlines has become a hot political potato since a Congressional investigation identified what it said was a cosy relationship between the FAA which inspects planes and staff at several airlines.
Some 500 flights were cancelled on Tuesday and another 1000 yesterday. More cancellations are expected today as the airline scrambles to inspect and even repair wiring in the wheel wells of planes.
Last night American was facing the prospect of collapsing confidence in its security procedures as it revealed that only 30 of the single-aisle planes had passed through the inspection process.
All day yesterday the airline was trying to notify passengers by emails and text messages about their cancelled flights. Cathy Sutton, 56, was at Los Angeles International airport LAX trying to reach Tampa to attend her daughter's wedding today. "I'm not happy. I've got a daughter getting married," she said.
American told her "everything was fine, that everything was on schedule, that there was no problem," the night before, she said.
"I'll be devastated, absolutely devastated." she said if she doesn't make it the wedding, "My daughter's on pins and needles. She's really upset."
The cancellations crippled the airline's major hubs in Dallas, Chicago, New York, St Louis and Austin where long queues of unhappy passengers formed. American has about 2,300 daily departures across the US every day.
The maintenance problem suddenly emerged when the FAA began a broad inspection of compliance with its directives. Dozens of planes were discovered to be inappropriately maintained at American, Southwest Airlines and United Airlines.
An spokesman for AMR which owns American, said around 100,000 passengers were affected by the problems. "We have obviously failed to comply with the airworthiness directive to the standards that the FAA requires," AMR Chief Executive Gerard Arpey said, "I take full responsibility."
"American will do whatever it takes to assist those affected by these flight changes," American chief executive Mr Arpey said. "This includes compensating those inconvenienced customers who stayed overnight in a location away from their final destination."
Shares in the company fell more than 11 percent yesterday afternoon.