(Associated Press) – Transportation Secretary Pete Buttigieg is warning airlines to be ready when wireless companies power up their 5G service next month.

Buttigieg told an airline trade group Friday that planes won’t be allowed to land in poor visibility if they lack equipment to avoid radio interference from 5G.

On July 1, AT&T, Verizon and other wireless carriers will be free to boost the power of their 5G signals.

Some aviation experts believe the signals could interfere with equipment that measures the height of planes above the ground.

But the Federal Communications Commission, which grants the 5G licenses to the wireless companies, says there’s no risk of interference.