This week: The ER descends into chaos as two planes collide midair and crash into the city below, Ray does his best to avoid Zoe, Abby and Luka aren't quite sure how to move forward with their relationship, Neela picked the best day to do her paramedic ride-along, Pratt does all he can for a conscious man whose heart won't start up again, and Clemente disagrees with the staff on how best to handle a mass casualty situation as his past begins to slowly catch up to him.