KEARNEY, Neb. (AP) — Two Cessna 172 airplanes are continuing the annual tradition of flying over the Central Platte River as part of the Platte River Whooping Crane Monitoring Project.

Two pilots and two observers will fly over 90 miles of the river Friday as part of the project, which was started in 2001. The project aims to collect data about how whooping cranes use the river and adjacent areas during their spring and fall migrations.

Ground observers protect the birds, which are on the federal Endangered Species List, from being disturbed and also collect data on features of the locations, length of stay and crane behaviors.

The Platte River Recovery Implementation Program is the main user of the data.