Question:  As of September 2017, the Delta Air Lines mainline fleet comprises 852 aircraft in service, merging with Northwest Airlines in 2009, Delta Air Lines operated an all-Boeing and McDonnell Douglas fleet; it incorporated into which company's Airbus aircraft into its fleet following the merger?
Sentence (from "Airbus"): In addition to its primary civil aeroplane business, the company has two divisions for other products and services: "Defence and Space" and "Helicopters", the latter being the largest in its industry in terms of revenues and turbine helicopter deliveries.
Relevant evidence: No