Sometimes airfares are just too good to be true.Southwest Airlines sent an online offer to about 10 million people in January 2013 for flights from Dallas to Branson, Mo., for a bargain price of $66. But fliers who tried to book the fares couldn’t find seats for the sale period — an error the airline blamed on a technical glitch.Unfair and deceptive practices, such as promoting fares that don’t exist, are by far the most common violation of passenger rights by the nation’s airlines, according to three years of U.S. Department of Transportation citation records.The Southwest violation was among more than 500 citations — resulting in $20.9 million in fines — issued from 2010 to 2013 to all airlines and travel agencies at a time when passengers were howling mad over new airline fees, cramped seating and mergers that cut service to smaller cities.A Los Angeles Times analysis of federal citations during that time period also found:• The most common citation for unfair and deceptive practices was a failure to disclose the full fare for a flight, including taxes.• The steepest penalties were imposed against airlines that mistreated disabled passengers.• Only about half the fines imposed by the Department of Transportation were collected, with the balance either suspended or directed to be used to improve airline services.In response to an outcry from passengers, the Department of Transportation cracked down on violators and adopted new passenger rights rules that took effect starting in 2010.In addition to requirements to advertise full fares, the new rules impose hefty fines on airlines that strand passengers on the tarmac for hours. Airlines must also refund checked-bag fees for lost luggage and give customers bumped from overbooked flights as much as $1,300 in compensation, up from the previous maximum of $800.These new rules focus primarily on the treatment of passengers — not on safety or mechanical issues, which are regulated by the Federal Aviation Administration.With renewed attention on passengers, the number of citations issued by the Department of Transportation nearly doubled. From 2010 to 2013, the number of citations imposed on airlines averaged 54 a year, compared with the average of 28 for the previous four years, according to federal citation records.Although passenger rights groups have welcomed the changes, some airline critics believe the new rules don’t go far enough and are calling for steeper fines to change the behavior of repeat violators.“I don’t think these fines do anything to mitigate or stop the bad behavior,” said Albert Rizzi, a blind traveler who was kicked off a US Airways plane in November 2013 when a flight attendant complained that his service dog had wandered into the aisle. “There are no consequences involved.”Of the 521 violations in 2010-13, the department cited airlines 181 times for violating rules of unfair and deceptive practices, such as Southwest’s nonexistent discount airfares to Branson, according to agency records.In each violation, the airlines and travel agencies signed consent orders to settle the allegations of wrongdoing raised by the Department of Transportation to avoid civil litigation.Ten months after Southwest was cited for promoting those fares, the department fined the Dallas-based airline $200,000 for running television ads touting another super-low fare from Atlanta that did not exist — another error, according to the airline.A rule requiring airlines to advertise the full cost of a flight took effect in January 2012. Since then, violations of the rule have led the federal agency to fine the nation’s airlines and travel agencies 57 times.For example, American Airlines advertised in February 2013 that children could fly “free” as part of a ski resort package. But the fine print said only the airfare charges were free — travelers still had to pay taxes and fees.Fort Worth-based American agreed to a $20,000 fine but disputed that it had broken any rules.Congress is now considering a bill, supported by most airlines, that would eliminate the full-fare rule, allowing airlines and travel agencies to advertise the fares and fees separately.The heftiest fines — nearly four times higher than the average penalty — were issued to airlines that neglected or mistreated disabled passengers, according to federal records.Delta Air Lines has been assessed the largest fine, $2 million, for 22 violations from 2007 to 2011.In one incident at New York’s John F. Kennedy International Airport, a disabled 79-year-old woman said she was left unattended in a terminal for more than two hours because she declined to pay a Delta worker $10 to push her wheelchair.Delta paid $750,000 of the total fine. The balance was credited to the airline for money it spent to improve services for disabled passengers, such as increasing employee training and investing in technology to ensure wheelchairs are provided to fliers who request them.Eight years earlier, Delta was fined $1.35 million for similar violations but was required to pay only $100,000 of the fine, with the balance either forgiven or credited to the airline for making improvements to services for disabled passengers.From 2010 to 2013, only $11.5 million of the $20.9 million in fines was paid to the U.S. Treasury, according to records.Rizzi, the disabled passenger who was forced off a US Airways flight, noted that his incident occurred only a week after the airline agreed to pay $1.2 million for allegedly discriminating against passengers with disabilities.“My sense is that these fines are meaningless to the airlines,” he said.American, which merged with US Airways in December, said it takes seriously its responsibility “to provide safe, reliable and convenient travel for passengers with disabilities,” and has committed to spend $2 million a year to improve service to disabled passengers.