The Boeing 737-400 is a single aisle, twin-engine jet. The major change of the 737-400 over the smaller 300 is a 3.05m (10ft 0in) fuselage stretch, consisting of a 1.83m (6ft 0in) stretch forward and a 1.22m (4ft 0in) plug rear of the wing. The stretch allows an increase in passenger seating. To cope with the increased weights, more powerful CFM56s are fitted. Other changes are minor, such as a tail bumper fitted to protect against over rotation at takeoff, something that could have become a problem due to the increased fuselage length.