Members of a fighter jet unit at the U.S. Marine Corps Air Station Iwakuni in Yamaguchi Prefecture frequently engaged in Top Gun-style stunts such as letting go of the controls, snapping selfies and even reading books.

The actions during training flights came to light in a report compiled by the Marine Corps and interviews with the Defense Ministry.

The report also revealed a collision between an FA-18 Hornet fighter jet and a KC-130 Hercules refueling aircraft off the coast of Kadena, Okinawa Prefecture, in April 2016.

The incident was not reported to Japan until now.

After the investigation, the Marine Corps dismissed four members of the unit, including its commanding officer.

“They broke the rules by not reporting the accident to Japan. If the accident was dealt with properly, measures might have been taken to prevent recurrences like one that occurred in Kochi Prefecture,” Defense Minister Taro Kono said during a news conference on Nov. 5.

Kono said he will demand the United States fully explain its actions.

In December, an FA-18 fighter jet from the Iwakuni unit and a KC-130 refueling aircraft of a different unit collided off the coast of Kochi Prefecture during a nighttime training exercise, killing six crew members.

This prompted the Marine Corps to compile the report, which was submitted to the Japanese government and other related parties in September.