In the U.S., gauges of airline delays, lost baggage and overbooked planes are all improving.
But that doesn't mean fewer complaints by airline passengers.
In fact, complaints filed against airlines in the U.S. rose 27% in the first nine months of the year, compared with the same period last year, according to data released Thursday by the U.S. Department of Transportation.
In the nine-month period, airline travelers filed 15,770 complaints, compared to 12,348 complaints filed in the same period in 2014, according to the federal agency.
The increase in complaints came despite improved numbers in many airline categories, including the rate of on-time arrivals, which rose to 86.5% in September, up from both the 81.1% on-time rate in September 2014 and the 80.3% mark in August 2015, according to the federal agency.
A flight is considered on time if it reaches the gate within 15 minutes of its scheduled arrival time.
The rate of mishandled or lost bags also dropped to 3.31 bags for every 1,000 passengers for the first nine months of the year, down from 3.70 bags per 1,000 passengers in September 2014.
Also, the rate of passengers who were involuntarily bumped off a plane that was overbooked dropped to 0.77 travelers per 10,000 passengers in the first nine months of the year from 1.04 travelers in the same period last year, the U.S. Department of Transportation reported.
The categories of complaints that rose the highest in the latest nine-month period include problems with fares, refunds, customer service, flight cancellations and flight delays, according to the federal data.
The complaints may be up because many airlines are offering fewer free amenities and shrinking economy seats to squeeze more passengers per plane, said Kate Hanni, founder of Flyersrights.org, a nonprofit passenger advocacy group with about 50,000 members.
"I don't think the flight experience has improved," she said. "People are stressed from the time they get to the airport and get through security and get on a plane with very tight seats."
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