PHILADELPHIA — A key piece of hardware that aviation experts and pilots said could solve the mystery in the fatal crash of the medical transport Learjet on Jan. 31 turned out to be useless.

bringing down several lanes and closing I-95 completely for some time. (This also generated a Wikipedia article.) This year, on January 31, a little further west on Cottman, a Learjet 55 medevac ...

Credit: NTSB The cockpit voice recorder did not record the moments before a Learjet 55 medical jet crashed earlier this year in a Philadelphia neighborhood, killing six people on the aircraft and ...