Prior to D'Haene, Leor Pantilat had the supported FKT on the JMT of 3d7h36m from Whitney Portal to Happy Isles (3d4h30m from Whitney Summit), August 15-18, 2014. It was Pantilat's first multiday effort & also his first run of 100+ miles. He carried a SPOT satellite tracking device which verifies his trip. A detailed trip report is on irunfar.com.
south to north
3d 7h 36m