Question: Which city are the headquarters of this airline founded in 1946 and privatized in 1969, which operates joint ventures with Delta Air Lines, located? 
Sentence (from "Delta Air Lines fleet"): Before merging with Northwest Airlines in 2009, Delta Air Lines operated an all-Boeing and McDonnell Douglas fleet; it incorporated Northwest's Airbus aircraft into its fleet following the merger and subsequently ordered further Airbus types.
Relevant evidence: No