Banning aircraft over Olympic Park costs only 0.04 percent of US airspace

Evidence

FAA airspace over the United States would be reduced by only four one-hundredths of one percent (0.04 percent) if Olympic National Park were to become off-limits to aircraft. — Gordon Hempton, John Grossmann, One Square Inch of Silence- One Man’s…, 1598

Categorization

• QUESTION: Worth verifying how this 0.04 percent was calculated and whether it accounts for flight-path rerouting costs.
• corroborated: 2 independent passages support this claim — Gordon Hempton, John Grossmann, One Square Inch of Silence- One Man’s…, 1598