No. 14 Frontier
                    On-Time Performance: 72.36%
                    Frontier had a toehold in the top 10 in 2011, when 79.16 percent of its flights were on time. But it has continued to slide: in 2012 Frontier dropped to No. 12, with a 77.93 percent record, and last year more than a quarter of its flights were delayed.