Southwest is the first major US airline to introduce such rules, but airlines all over the planet are tightening restrictions in the interest of fire safety.
It might be a good idea to start charging your phone before you travel—airlines around the world are now tightening their rules surrounding portable chargers and power banks.
If you’re traveling via Southwest Airlines in the future, you’ll need to keep your portable charger visible anytime you’re using it, which means no leaving your phone to charge in your baggage or the overhead storage compartment.
The airline stopped short of a full ban, however, and you can still bring up to 20 spare batteries on your next Southwest flight. You are also still allowed to store these in your hand luggage, just not use them.
