My wife has a carry one bag with a built in battery pack. It is so you can charge your phone off the battery. We gate checked it on a recent trip and the first thing the gate agent checked was IF we had taken that battery out of the luggage.
The last thing they want is one of those batteries catching fire down in the cargo hold. It could literally bring the plane down.
“The last thing they want is one of those batteries catching fire down in the cargo hold.”
Because that has happened in the past. 😱