There are dozens of U.S. military bases on Honshu, with thousands of dependents. At this point the evacuation order is voluntary, it’s called “military-assisted voluntary departure.”
The plan involves taking military dependents to Korea. Because the it is a voluntary evacuation, commercial flights would be used. There is a potential for thousands of people wanting out, in that case they will start using military transports.
Potassium Iodide pills are being shipping in, mainly for JSDF troops, and U.S. personnel involved in fighting to keep Fukushima Daiichi plant cool.