Read the F-35 Accident Report

Here is a copy of the Accident Investigation Board report (click link) released to Aviation Week from the June 23, 2014 "catastrophic" F135 engine fire that caused more than $50 million worth of damage to an F-35A prior to takeoff. The fire in the Pratt & Whitney engine also prompted a grounding that prevented the F-35B from making its international debut last year at the Royal International Air Tattoo and Farnborough Air Shows. 

credit: USAF AETC

You'll also see pictures of the accident damage and diagrams of the failure in the 3rd stage integrally bladed rotor. The cause was friction inside the IBR prompted a "catastrophic" failure and fire. The pilot egressed safely and the aircraft will now be used for spare parts for other aircraft.