After measuring minute elevation changes on runways at 15 coastal airports around the United States, researchers found that of airport runways sinking, or subsiding, San Francisco (SFO) tops the subsidence chart at nearly 10 millimeters (0.4 inches) per year, while Los Angeles International Airport (LAX) is the slowest. America’s crumbling roads and sagging bridges have garnered attention over the past few years, prompting the passing of the Infrastructure Investment and Jobs Act in 2021. But the nation’s runways are also feeling their age, posing serious hazards to the millions of travelers who fly every day, researchers say.