The head of the US Federal Communications Commission warned on Wednesday that there is not enough room in the airwaves for the “explosion” in wireless data traffic, setting the stage for a big realignment of spectrum usage as the government tries to help mobile carriers keep up with consumer demand.

“The biggest threat to the future of mobile in America is the looming spectrum crisis,” said Julius Genachowski, the Obama administration appointee who took over as head of the five-member FCC in late June.