A USB Killed is a USB Drive that has been modified to deliver an electrical surge that can damage or destroy hardware when the altered thumb drive(modified USB Drive) is inserted into a computer's USB port. The modified drive essentially commands the computer's onboard capacitors to rapidly charge and discharge repeatedly. If left alone the repeated overcharging will overload the USB port and physically destroy the computer's electrical system.
What's happens if someone plugged a USB killer into an airplane
USB slot USB ports on commercial flights, or any form of public transport for that matter, are charging ports only. Charging ports use the USB data lines only to signal to the connected device what charging modes are available. One common basic charger configuration is that the data lines are just shorted. As USB killers are designed to overload the data lines, a USB killer connected to one of these ports is not going to damage anything but itself, and/or possibly just the port it’s connected to.