John Pennington left his vehicle and is thought to be on a yellowish bike.

A 40-year-old guy has gone missing in the Grand Canyon, sparking a hunt by the National Park Service.

Pennington left his car at Yaki Point on or about Feb. 23 and is thought to be traveling independently, maybe on a yellowish bike, the park service said.

Grand Canyon spokesperson Joelle Baird said Monday,"Yesterday and ongoing now our aviation team will continue airborne hunt reconnaissance flights"

Rangers ask anybody who might have seen Pennington or even the yellow bike to telephone the park agency's Investigative Services Branch Tip Line in 888-653-0009.

A family spokesperson urged anyone with information to call the tip linetold ABC News,"our appreciation and thanks to the NPS and the regional government to their efforts."

Pennington is called a white guy with hazel eyes and brown hair.

The bicycle, a 2005 Suzuki, comes with an Ohio license plate number GSX-R600.