"WestJet pioneered low-cost flying in Canada with a growing fleet of the world's most popular jetliner and has emerged as a leader among the world's airlines," said Kevin Schemm, Boeing Commercial Airplanes vice president, North America Sales. "We value our partnership with WestJet and its continued endorsement of the Next-Generation 737."

WestJet also has announced a plan to reschedule 16 leased and direct-purchase airplanes. "The new order of Boeing 737-700s will enable us to continue serving our guests with one of the most modern fleets in the air," said Sean Durfy, WestJet president and CEO. "At the same time, we'll have enhanced flexibility to deliver on our vision of becoming one of the top five airlines in the world by 2016."

Including today's order, WestJet has 54 additional Next-Generation 737s scheduled for delivery.

Nearly 120 customers around the world have ordered more than 5,000 Next-Generation 737s. Boeing has more than 2,100 unfilled orders for the Next-Generation 737 valued at more than $158 billion at current list prices.

Earlier this year, Boeing announced performance enhancements to the Next-Generation 737, which will reduce fuel consumption by 2 percent by 2011 through a combination of airframe and engine improvements.