CHICAGO--(BUSINESS WIRE)-- Fitch Ratings has upgraded the issuer default rating (IDR) of United Continental Holdings, Inc. (UAL) and its two airline operating subsidiaries to 'B' from 'B-'.

The upgrade follows a year of significant debt reduction and strong free cash flow generation since the closing of the United-Continental merger on Oct. 1, 2010. In the face of heavy fuel cost pressure during the first half of 2011, UAL has consistently reported industry-leading revenue per available seat mile (RASM) growth while funding heavy debt maturities out of internally generated cash flow.