United Airlines, the second largest carrier in the US, has been fined by the Department of Transportation for violating rules that protect passengers with disability, and for making travellers wait on delayed flights for more than three hours. The airline acknowledged the fine and vowed to create better infrastructure for disabled passengers.

The Department of Transportation (DOT) fined the carrier $2.75m (£1.88m). In a statement, US Transportation Secretary Anthony Foxx said: "It is our duty to ensure that travellers with disabilities have access to the services they need, and that when significant tarmac delays happen, travellers are not left on the plane. We will make sure that airlines comply with our rules and treat their passengers fairly."

DOT said it received a large number of complaints related to ignorance or mistreatment of disabled passengers in the last year. At the forefront was an incident in October when a passenger with cerebral palsy was forced to crawl out of a United flight, as crew failed to provide the man with a special wheelchair. Although the airline publicly apologised for the incident, it was heavily criticised.

According to federal guidelines all carriers are required to allow wheelchairs and other mobility aid in the flight for passengers. They can be stored in the baggage compartment if there is no room in the cabin. But DOT investigators found that United repeatedly failed to provide wheelchairs and other mobility aid to passengers in a timely manner.

Taking stock of the situation, United Airlines said that it is testing a new app via which passengers and crew members will be able to order wheelchairs on planes and terminals more effectively. "We expect this to greatly improve our ability to have wheelchairs where they need to be, when they need to be there, so that our customers can get on their way home or to their next destination with ease," said Jon Roitman, senior vice president of airport operations at United.

As for the tarmac delay related fines, commercial airlines in the US are barred from holding passengers on a flight, for more than three hours, without giving them the option to disembark. The time limit extends to four hours for international flights. United, however, was found to have kept passengers on board for up to four-and-a-half hours for flights to and from Tampa, Washington, Houston and Paris.

In 2011, DOT fined United $20,000 for providing inaccurate information to passengers about how much compensation they could potentially receive for lost, damaged or delayed baggage on international flights. In January last year, the Federal Aviation Administration sought a fine of $1.3m from United, claiming the carrier violated rules about shipping hazardous material often by inaccurately describing the amount of the cargo.