(NEWSER) – It could have been the deadliest plane crash in the world to date, but thankfully, one pilot's quick reflexes saved the lives of hundreds of passengers on two planes that were headed straight toward each other. Last month, a United plane with 295 people onboard was cruising at 33,000 feet over Hawaii when its pilot spotted a US Airways plane that "just popped right at our altitude." He initiated an abrupt 600-foot emergency descent to avoid a head-on collision. Experts say he had just 15 seconds to act, which meant passengers were caught without warning as the plane made its dramatic plunge in just seconds. "Passengers started screaming," says one. "I was weightless. We all were." Newsy reports: