How to Arrange Travel Out of Japan
From the Department of State:
The U.S. Embassy in Tokyo informs U.S. citizens in Japan who wish to depart that the Department of State is making arrangements to provide transportation to safehaven locations in Asia. This assistance will be provided on a reimbursable basis, as required by U.S. law. U.S. citizens who travel on US government-arranged transport will be expected to make their own onward travel plans from the safehaven location. Flights to evacuation points will begin departing Japan on Thursday, March 17.
Find more details on safehaven travel.