The top leaders of a Japan-based Marine Corps F/A-18D Hornet squadron were fired after an investigation into a deadly mid-air collision last December found that poor training and an "unprofessional command climate" contributed to the crash that left six Marines dead, officials announced on Monday.

Five Marines aboard a KC-130J Super Hercules and one Marine onboard an F/A-18D Hornet were killed in the Dec. 6, 2018 collision that took place about 200 miles off the Japanese coast. Another Marine aviator who was in the Hornet survived.