Only 58 % of United Airlines flights were on - time in September . Fuel disputes and maintenance issues contributed to the steep rate drop . Overall , the airlines ' on - time rates improved over August , but dropped from August 2011 .
Only 58 % of American Airlines flights were on-time in September . Labor disputes and maintenance issues contributed to the steep performance drop . Overall , U.S. airlines ' on-time rates improved over August , but dropped from September 2011 .