Five water-dropping planes and another five helicopters took off at first light on Monday to help hundreds of firefighters battling a major wildfire west of Athens, a day after a mid-air collision between two firefighting helicopters killed two crew members. The collision laid bare the danger at the most volatile front of Europe’s wildfire emergency. The two crew members, one Greek and one Danish national, died when their helicopter collided with another near the seaside area of Psatha while tackling the fire that started Friday morning. The blaze raged through pine forests and scrubland through the weekend, whipped by gale…