To find out the cause of the malfunction on the iPhone, the device was shipped to the FAA and a misplaced screw was discovered inside the unit's battery cavity. The Apple iPhone's owner had the screen on his phone replaced, but not by an authorized iPhone repair center. The center accidentally failed to properly replace the screw which was most likely holding the model's 30 pin connector in place. The loose pin shorted out the battery terminals which caused the smoke and red glow.
The repair center also failed to replace a screw that fastened the main board of the device, put two screws used to fasten cable in the wrong spots, damaged the adhesive that keeps the main board in place, removed the two indicators used to determine if a liquid spill damaged the unit and deformed a metal clip used for the battery.
In an understatement, the ATSB said that its findings indicate, "a lack of appropriate quality control on behalf of the unauthorized repair facility". The agency also noted that this is the reason why devices using a lithium-ion battery should be carried on a plane rather than checked in as luggage.
The damage to the Apple iPhone (L) was partially caused by a faulty repair that left a screw in the battery cavity, according to the FCC, where it shorted out the battery terminal