In at least the third such incident in less than two years, an airline is facing a fine from the U.S. Department of Transportation over complaints filed by passengers with disabilities.

Federal officials said Friday that they are fining Spirit Airlines $100,000 after an audit of the Florida-based discount carrier’s records for 2009 and 2010 uncovered a failure to properly account for disability complaints.

Airlines are required to provide an annual report to the Department of Transportation documenting disability complaints sorted by type of disability and the alleged problem. But Spirit did not properly account for the grievances and the airline “failed to provide adequate responses to a vast majority of the disability-related complaints it received,” the Department of Transportation said.

“Our rules on how airlines handle disability-related complaints are designed to help us ensure that passengers with disabilities are treated fairly when they fly,” said Transportation Secretary Ray LaHood. “We will continue to make sure carriers comply with our disability rules and take enforcement action when they do not.”

Spirit is not the only airline to be fined in recent years for its handling of passengers with disabilities. The Department of Transportation slapped AirTran with a $500,000 penalty in 2010 and Delta Air Lines was assessed $2 million in 2011 over disability violations.

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