4,293 737NG aircraft have been delivered (as of December 2012). More than 6,300 have been ordered by airlines. Southwest Airlines has more 737NGs than any other airline. Ryanair, a low-cost airline from Ireland, also has a lot of 737NGs. The only planes Ryanair has are 737-800s. The main rival of the 737NG family is the Airbus A320 family. The Boeing 737 MAX will eventually replace the 737NG.