Noise impact falls off dramatically the higher a plane goes, which is why flight charts are full of markings requiring pilots to stay 2,000 feet above sensitive bird-nesting areas, 4,000 feet above wilderness hiking or canoeing areas, 14,500 feet above the most scenic parts of the Grand Canyon—so high that pilots are required to use oxygen masks there. (So why is the Grand Canyon still noisy? Because commercial tour operators are allowed to fly lower.)

Gordon Hempton, John Grossmann, One Square Inch of Silence-…, loc. 1637