ACCIDENT

Dust to Blame for Marines’ Crash?

Officials said on Thursday that it could weeks to determine what caused two helicopters to collide in midair Wednesday night during routine military exercises along the Arizona-California border. Six of the dead were based at Camp Pendleton in California, and one was from a base in Yuma, Ariz. The skies were clear, but a spokesperson from the Yuma base said visibility may have been severely limited by dust, referred to as a "brown out," created by the helicopters landing and taking off. The crash is one of the Marine Corps' deadliest aviation-training accidents in years.