a radio spectrum that could bleed over and interfere with a plane s radar altimeter. those altimeters bounce a signal off the ground to give pilots their precise distance to the ground 50, 40, 30 reporter: critical for landing in poor visibility warning of potential interference, the faa had told pilots they would not be able to use altimeters at more than 80 airports near 5g sites, including large airport hubs in houston, dallas, l.a., new york, chicago, and seattle the airlines warned that would lead to massive delays, diversions and cancellations as soon as wednesday. the faa has to go airport by airport, runway by runway and do an analysis to clear these runways at airports so that we can safely fly. reporter: but the cell phone industry, which already delayed the rollout twice and says 5g is safe at&t today took aim at the faa saying we ar frustrated by the faa s inability to do what nearly 40 countries have done, which is to safely deploy 5g technology without disruptin