ATLANTA, Nov. 27, 2012 /PRNewswire/ -- Corporate travel managers again rated Delta Air Lines No. 1 in this year's Business Travel News Annual Airline Survey. The airline ranked first among all carriers in key categories including: Value of Relationships with Account Managers and Sales Representatives; Distribution Channels; Complaint/Problem Resolution; Quality of Customer Service; and Networks, Airline Partnerships and Frequencies. (Logo: http://photos.prnewswire.com/prnh/20090202/DELTALOGO ) Delta also earned the distinction of being the first carrier in the survey's 15-year history to be rated No. 1 in all 10 categories. "This award reflects how our most important corporate customers continue to embrace the $3 billion we are investing to improve our flying experience while highlighting the hard work and service commitment of our 80,000 employees," said Ed Bastian, Delta's president. "Recognition from our most frequent customers is the most important recognition we can receive. To finish first a second year in a row and in all 10 service delivery categories is a great acknowledgement of our efforts to build a better airline." "We offer our congratulations to Delta Air Lines for their strong showing across all the categories we measured in our latest Annual Airline Survey. Their efforts over the past several years are clearly resonating within the business travel community," said Tim Reid, vp-Group publisher, The BTN Group. Through 2013, Delta is investing more than $3 billion in airport facilities, global products, services and technology to enhance the customer experience in the air and on the ground. Customer improvements include a $1.2 billion facility renovation at New York-JFK's Terminal 4, a $160 million project to modernize LaGuardia's Terminals C and D, as well as updating the Los Angeles airport jet bridges, baggage claim hall and ticket counter areas and other facility improvements in Salt Lake City and Seattle. Onboard Delta is adding full flat-bed seats to all BusinessElite cabins and enhancing in-flight food, beverages, entertainment and amenities. In 2012 Delta expanded its popular Economy Comfort seating and completed Wi-Fi access to its fleet of more than 800 two-class aircraft. Beginning in 2013, customers will benefit from additional productivity and entertainment options when the airline adds streaming content to all two-class aircraft and satellite based Wi-Fi to its fleet of international widebody aircraft.