A gas explosion caused a hot air balloon in Egypt to plummet to the ground, killing 18 of the 21 people onboard. It’s the deadliest hot air balloon crash in more than 20 years. The hot air balloon was part of a popular tourist attraction, in which visitors would fly over scenic farmland and ancient temples near the banks of the Nile River. Officials in the Luxor province where the crash occurred have announced they are temporarily banning all hot air balloon rides while they further investigate the cause of the crash …