On Wednesday, American Airlines explained the restrictions, writing in a statement to CNN:
"Smart bags, also known as smart luggage, have become more popular over the last few months, and they are expected to be a popular gift this holiday season. However, smart bags contain lithium battery power banks, which pose a risk when they are placed in the cargo hold of an aircraft."
Smart bags, a popular product and outgrowth of the internet of things, typically use a USB port for phone and other battery charging needs and a GPS tracking system that helps people keep track of their valuables. Sometimes, they skate on the ground like BB-8 to help people avoid the strain of carrying heavy bags.
The potential of a fire in the cargo hold is the primary concern for airlines. Carries will let customers check their bags if the batteries are removable, but in the case of many widely used smart bags, the batteries are a permanent component of the luggage. American, Delta, and Alaska all said they no longer allow smart bags with non-removable batteries.