“We’ve missed you,” Egypt’s ministry of tourism says in its new advertising campaign , a plaintive plea for summer visitors from wealthy countries in the Persian Gulf. That is putting it mildly. For three years now, political turmoil has scared many travelers away from Egypt, leaving millions of people whose livelihoods depend on visitors desperate for any sign of an end to the most sustained tourism crisis anyone here can recall. At Cosmos , a 37-year-old tour company in Cairo that used to serve up to 30,000 customers a year, Khaled M. Ismail, the company’s director of operations, said he had not booked a single visitor since May 2013. The company’s once-hectic headquarters are deserted most of the time: Employees come in only once a week, to pay the bills. “We’re not expecting any business until 2015,” Mr. Ismail said, sitting alone in his office one recent […]