Delta Air Lines may hub its fleet of Bombardier C Series jets out of New York and Los Angeles, according to a memo sent to pilots. The memo, obtained by Bloomberg News, suggests the carrier is eyeing the cities as the main bases for the 108-seat single-aisle plane with Dallas also on the cards. Delta ordered 75 Canadian-made CS100s, the first of which are due to arrive in the spring of 2018, with options for 50 more. The airline plans to deploy the aircraft on short- to-medium-haul routes and expects its comfortable interior, featuring some of the widest seats of any narrowbody aircraft and big overhead bins, to be a winner with passengers accustomed to smaller planes. The aircraft is powered by Pratt & Whitney’s PW1500G geared turbofan engine and is forecast to deliver a 20 percent improvement in fuel efficiency compared to similar aircraft. The order was a lifeline for Bombardier but upset US aerospace giant Boeing, which claims its development was subsidised by the Quebecois and Canadian governments. Boeing has accused Bombardier of selling the aircraft to Delta at below the cost of production and its complaint of unfair competition has prompted an investigation by the US Commerce Department. But Bombardier has argued Boeing does not produce 100-seater aircraft that compete against the CS100. The decision to invest in the new aircraft was part of a strategy by Delta to reduce costs and boost customer satisfaction by replacing inefficient, older aircraft. Read: Branson cedes control in bold alliance between Virgin Atlantic, Delta and Air France-KLM. It has retired 280 50-seat regional jets and more than 130 older, narrowbody planes since 2009 for an 8 percent reduction in fuel consumption per passenger mile. Deltas has one of the oldest fleets of any US carrier with an average age of 17 years. Swiss International Airlines launched the C Series into revenue service in July last year. Bombardier has 360 orders for the CS100  and the bigger CS300.