Just as a delta is a symbol for change in math, Delta Air Lines symbolizes the changing mathematics of the airline industry. Delta became one of the world's largest airlines by traffic after its acquisition of Northwest Airlines in 2008. Through its regional carriers, the company serves around 320 destinations in more than 60 countries. It also operates a mainline fleet of over 700 aircraft and manages maintenance, repair, and overhaul (MRO) and cargo operations. Delta is a founding member of the SkyTeam marketing and code-sharing alliance, which includes the carriers Air France, KLM and Alitalia.