Abstract: A leading edge arrangement includes a fixed wing portion 10, a slat member 18 slidably mounted with respect thereto by an arm 14. The arm 14 is provided with an internal trackway 15 and external cam surfaces 16' and 16", the trackway co-operating with roller bearings 12 on the fixed wing portion and the cam surfaces co-operating with respective roller bearings 13' and 13" on the fixed wing portion. The profiles of the trackway and cam surface are selected so that from a stowed cruise condition the slat member initially moves to a take-off setting along a path in which the ratio of downward deflection to extension movement is low, and subsequently moves to a landing setting along a path in which the said ratio is high. A modification is also described in which the rearward heel of the slat member which is exposed when the slat is extended is formed of a flexible panel portion, so that it may blend smoothly with the remainder of the rearward surface of the slat member.