Google Earth view of Japan's Fukushima Power Plant

In the event that the situation at Fukushima Daiichi nuclear power plant in Japan worsens, the US Federal Aviation Administration stated it is prepared to take air traffic measures that would include rerouting planes. 

Officials at the FAA have taken the lead in the global response to the ongoing situation at Fukushima if the nuclear crisis worsens. Currently there is ano-fly zone around the plant site, which is preventing planes from getting close to the areas. The concern is that if an aircraft gets close enough, it may spread contamination further.

Commenting on the situation, FAA officials said: "If this scenario were to occur, we anticipate that the US
carriers and other operators flying in the affected airspace would
revise their flight schedules."