delta air lines is currently the largest operator of the 717, flying nearly 60 percent of all in-service jets, but did not purchase any of the planes new from boeing. in 2013, delta began leasing the entire fleet of 88 jets previously operated by airtran airways from southwest airlines, who had purchased airtran, but wanted to preserve its all-boeing 737 fleet rather than taking on another class of aircraft. in 2015, blue1 announced it would sell its 717 fleet, with five jets going to delta air lines and four going to the third largest operator of the type, volotea. for delta, used boeing 717 and md-90s allowed them to retire their dc-9s while also being cheaper to acquire than buying brand-new jets from airbus or boeing. unlike other mainline us legacy carriers, delta has decided that its best path to profitability is a strategy that utilizes older aircraft, and delta has created a very extensive mro (maintenance, repair and overhaul) organization, called techops, to support them.