Boeing and Southwest Airlines said the airline converted 79 options into firm orders for Next-Generation 737-700s, bringing the airline's total past and future Boeing orders for 737-700s to 370 airplanes. The newly ordered planes will be delivered between 2007 and 2012 in a deal worth approximately $4.5 billion. Southwest now has 140 undelivered 737s on order from Boeing. Southwest operates an all-Boeing fleet of 452 737s, including seven airplanes delivered so far this year.