United Continental Holdings Inc. reported a "measurable decline" in demand for Japan-bound flights and signaled some flying may be cut as the crisis deepens at the country's earthquake-damaged nuclear plant.

"We are monitoring the markets closely and will continue to provide the level of service that is warranted by demand and which can be operated safely," a spokesman, Andrew Ferraro, said Wednesday. He declined comment on whether seating capacity to Japan will be trimmed.

A full schedule of 183 weekly departures to Japan for United Continental's United and Continental brands remains intact except for a route between Guam and Sendai, where the airport was damaged, Ferraro said in an e-mail.