The convex bladed aircrew knife was believed to pose too great a threat of accidentaly puncturing floatation devices in the hands of aircrew that were only allowed to use blunt-nosed scissors in real life. Hence the concave blade on the trditional version pictured above.
It could, given enough time, cut paracord and webbing, but it was really best for sharpening pencils, which we weren't allowed to carry in the aircraft.