Were U.S. Highways Actually Built to Double as Airstrips?

The widely circulated "fact" that U.S. highways were designed as emergency airstrips is mostly just an urban legend, despite its widespread recognition (many people seem to believe it) and its long-standing nature (the exact origin is unclear, but it can be traced back to 1940s legislation). On the surface, the idea appears both reasonable and puzzling. Surely, a military aircraft should be able to land on a wide road in an emergency! But then, what about roads that are winding, hilly, or otherwise not suitable for landing? And what about all the vehicles already on the road, with no warning of an emergency landing?

The creators of this urban myth did consider some of these concerns. For example, not the entire road is meant to serve as an emergency runway—just 1 mile (1.6 kilometers) for every 5 miles (8 kilometers). This ratio supposedly covers curves, changes in elevation, and heavily populated areas. Like most urban legends, there is a historical kernel of truth. The 1-in-5-mile rule stems from misunderstandings or misquotes of the 1941 Defense Highway Act, the 1944 Federal-Aid Highway Act, and the 1956 Federal-Aid Highway Act, depending on the source.

While all three of these acts exist, none actually include such provisions. The Defense Highway Act established flight strips near highways, primarily for military use. The first Federal-Aid Highway Act nearly added another flight strip program but ultimately didn’t, and it was absent from the second Federal-Aid Highway Act as well [source: Weingroff].

No law has ever been passed to support this, and moreover, the idea wouldn't work in practice. Since an emergency landing on a highway would only occur in an extreme and hypothetical scenario where planes couldn't even reroute to a nearby airport, there's no way local authorities could clear the highway in time for a safe landing.

So, what’s the alternative if an emergency occurs and planes unable to reach their intended destination need to land quickly? The most viable options are small municipal and private airports. Military bases also serve as another option. Across the country, there are underutilized and lesser-known runways (primarily not for public commercial flights) that could serve as a practical landing site in the event of an emergency caused by war or terrorism.