Boeing engineers completed the first series of wind tunnel tests for the 737 Multi-mission Maritime Aircraft (MMA) program on Nov. 5, 2004. Low-speed wind tunnel tests began on an 11 percent scale model of a 737 MMA on Oct. 28 in Boeing's 20 ft. by 20 ft. subsonic wind tunnel facility in Philadelphia , PA. The facility is the largest privately owned wind tunnel in the United States and can subject models to wind speeds up to 215 knots. The engineering team looked at a variety of unique features in addition to the basic stability of the aircraft including weapons bay door open, flaps down, landing gear down to simulate takeoff and landing conditions. An estimated 3,000 hours of wind tunnel time will be logged to develop the 737 MMA.