Worst single aircraft crash was JAL 123, a domestic-configured 747SR. 520 out of 524 died. A botched repair on the rear pressure bulkhead seven years previously gave way and the explosive decompression blew off the tail fin and severed hydraulic lines for all four systems.

Most passengers ever on a jet was 1,122 on an El Al flight as part of Operation Solomon in 1991. Edit: Clarification: most people ever carried on a jet and thus the biggest potential crash toll. However, it did not crash.