The world is shifting — literally.

The earth's magnetic field shifted magnetic north. It's always moving. Over the decades, magnetic north moved enough that manual compasses have to be recalibrated, paper maps may be outdated, and airport runways have to be renamed.

"The earth moves, and as that molten core shifts, you can shift a little bit for pilot safety, because it’s always all about safety, you have to change those runway designations," said Brian Kulpin with the Reno-Tahoe Airport Authority.

Runway 1634 right is now 1735 right. The 16 painted on the runway was repainted a couple of weeks ago to 16 R.

The numbers identify runways but also tell pilots the magnetic heading of the runway — how many degrees off magnetic north.

Pilot Jonathan Hartness said electronic cockpits are updated automatically.

"It’s a very easy change, it’s almost seamless for those with a glass cockpits with a lot of avionics, electronics.," he said.

Airports across the country are changing their runways. Hartness said he saw Florida update their runways a couple of weeks ago.

4.3 million people a year fly through Reno's airport. Pilots fly 150 flights a day from the airport.

"They’re all using these runways so for safety, you have to have the right designation, it helps all those aircraft line up and be and be controlled by the air traffic control tower," Kulpin said.

Changes most people won't even know about, but important to keep people safe.