When an airplane lands at an airport, in order to reduce the taxiing distance, the tail of the airplane opens a reduction parachute at the moment of touching the ground to increase the resistance and make the airplane slow down and stop quickly. There is an airplane with a mass of 9000kg and a horizontal speed of 700kN /h when landing. After the test, after the reduction parachute is opened, the total resistance of the aircraft is proportional to the speed of the aircraft(the specific side coefficient is HK =6.0 x 106). From the landing point, what is the longest distance of the aircraft?(Note kg stands for kg and km/h stands for km/h.)