An investigation by the Tampa Bay Times has found that planes operated by Allegiant Air are four times as likely to fail during flight as those flown by other major U.S. carriers. Forty-two of the budget airline’s 86 planes broke down in mid-flight at least once in 2015. And while most U.S. airlines reported about three unexpected landings due to mechanical problems for every 10,000 flights, Allegiant reported 12 per 10,000.

To compare airlines, the Times built a database of more than 65,000 records from the Federal Aviation Administration. They connected flight records with documents that showed mechanical problems at 11 of the largest carriers in the country, including Southwest, Delta and United. 

In interviews with reporters, Allegiant executives did not dispute the paper’s findings. The company plans to phase out its aging fleet of McDonnell Douglas MD-80s and buy new Airbuses.