A group of American fighter pilots have been severely reprimanded for taking selfies and reading books in the cockpits of their jets, in a report into a crash last year which killed six people.

The behaviour of the Japan-based pilots, who fly out of the Marine Corps Air Station in Iwakuni, was investigated as part of the review into the December 2018 mid-air collision.

The internal US military report, handed to the Japanese government at the end of September, condemned the unprofessionalism within the Marine All-Weather Fighter Attack Squadron 242.

They found the unit suffered from “inadequate oversight of training and operations” and an “unprofessional command climate.”

“Examples of such unprofessionalism included prescription and over-the-counter drug abuse, excessive alcohol consumption, adultery, orders violations, and failures in following fundamental principles of professional aviation training and operations,” the report said.