The US Department of Transportation (DOT) has fined Frontier Airlines, American Airlines and Delta Air Lines for violating several rules aimed at protecting consumer rights.

Frontier Airlines has been charged a $400,000 penalty for violating DOT’s oversales and disability rules.

According to DOT, Frontier failed to seek volunteers before involuntarily removing passengers from the aircraft and was unable to provide them with the required written notice describing their rights.

"The airline was also failed to provide proper compensation to passengers in a timely manner, which is a violation of DOT rules."

The airline was also failed to provide proper compensation to passengers in a timely manner, which is a violation of DOT rules.

Frontier also failed to provide passengers with a disability prompt and adequate wheelchair assistance in boarding and disembarking aircraft, as well as while moving within the terminal.

The airlines did not even adequately respond to complaints filed by passengers with disabilities, said DOT.

The department has asked American Airlines to pay a $250,000 fine for failing to make timely refunds to passengers.

Delta Air Lines has been $200,000 for filing inaccurate baggage reports to the DOT.

The department noted that Delta underreported the number of mishandled baggage reports received from passengers. This has made the airline’s ranking in the Department’s Air Travel Consumer Report seem better than it was at various times.

Following the DOT order, all three carriers have expressed positive intention to pay their respective fines and improve their future consumer protection services, reported AP.