Federal transportation data shows Frontier Airlines is no longer the most-complained about airline in the country.

The Denver Post reports complaints against the company in May were being reported more than twice as often as the same time in 2014, but decreased by 5 percent from April.

The airline's CEO stepped down in May as the company started billing itself as a bargain carrier and complaints rose.

President Barry Biffle said at the time that leadership is working to solve operational issues. He said the schedule is built to be more resilient and communication companywide has been a focus of improvement.

Federal data released Tuesday shows the frequency of on-time flights is also improving.