The deputy commander of an elite group of U.S. Marines says it is just coincidence that a battalion has suffered two fatal aircraft crashes in just over two years.

Six Marines and a Navy corpsman in a unit of the Raiders died in a crash Monday in Mississippi, on the way to a training exercise. In March 2015, seven members of the same North Carolina-based command were killed in a helicopter crash off Florida.

Marine Special Operations Command Deputy Commander Col. Stephen Grass said Friday that these crashes are just coincidences and won't deter the unit from its mission.

The current incarnation of the Marine Raiders was formed in 2006 with historic links to World War II commando units, amid the global war on terror.