The statement that the 727 and 707 have leading edge flaps was correct BUT they also have leading edge slats on the outboard sections of the wing. They are both hydraulically actuated. There is another leading edge device that has been used called a leading edge droop. The Navy FJ-4 had them. All these devices were installed to lower stall speeds and increase lift at lower airspeeds. Landing airspeeds had to be increased without the leading edge devices extended.