The bags have a battery built in, along with a complete charging system: Apple connector, Micro- and Mini-USB connectors and an on-board USB port for charging up to 4 devices at once.
Atlantic Southeast, which was sold to Skywest Airlines by Delta in 2005 but continues as Delta's connector partner, tends to get short shrift during weather delays by an Air Traffic Control system that would always rather delay flights with relatively fewer people on them.