A terrifying scene unfolded over Greece on Sunday as two firefighting helicopters collided in midair while crews battled a fierce wildfire west of Athens. Moments later, flames erupt and one of the helicopters plunges toward the ground. Firefighting aircraft are often pushed into dangerous conditions when flames move quickly and ground crews cannot reach threatened areas fast enough. Another blaze in central Greece forced roughly 500 people, many of them tourists, to be moved out of danger on Friday. Investigators will now have to examine flight paths, communication, weather conditions, and the final movements of both helicopters.