Boeing 737 Next Generation
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.