Since its first flight over 40 years ago, more than 7,000 of these airplanes have been built.  Boeing has made improvements over the years to make this one of the most fuel-efficient aircraft in its class.  The newest models of the 737 seats up to 215 passengers, and it can carry passengers non-stop from New York to London.  Some of the recent success for the 737 has come from the addition of blended winglets.  This modification to the end of the wing allows for a twenty percent increase in fuel efficiency.  The winglets also allow for better climb performance.  Boeing has some new improvement on the interior of the aircraft.  These improvements will improve the passenger’s experience, as well as increase the amount of overhead bin space.  With these improvements Boeing continues to keep the operation cost low and demand for the aircraft high.