The crash was reported at about 12:30 pm in an area covered by sage and grass near the airport in Arco, the Butte County Sheriff’s Office said.
Arco is about 70 miles (113 kms) west of Idaho Falls.
The National Transportation Safety Board and the Federal Aviation Administration were notified about the crash. The cause is under investigation, the sheriff’s office said
The names of the pilots involved have been withheld until their families could be notified, officials said.
