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.

A medical transport jet crashed on Friday in northeast Philadelphia. The Learjet 55 had six people on board when it went down shortly after departing Northeast Philadelphia Airport, according to ...

And while the doomed Learjet 55 was in contact with an air traffic control tower, "there were no distress calls received from the flight crew," the report said. The fiery crash killed six people ...

The NTSB's early investigation into the Jan. 31 crash revealed little about what caused the Learjet 55 to go down seconds after taking off from Northeast Philadelphia Airport. The jet slammed into ...

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 ...