A map showing thousands of flights in the air over the US has raised questions over why so many planes are still being allowed to fly across the country.
The map, which was posted to Twitter by global flight tracking service Flightradar24, shows the US covered in tiny yellow planes that represent flights over the country.
"Of the 4800 flights we're currently tracking worldwide, two-thirds are seen in this image," Flightradar24 said about the image.