The security measures on aircraft belonging to Israeli airlines and around them during takeoffs and arrivals abroad have been significantly boosted over the past few days for fear that Hizbullah would act on its promise to avenge the February assassination of its top commander Imad Mugniyah. The number of armed security guards on some of the flights to several destinations has been increased, as was the number of guards surrounding the plane after the landing and before the takeoff. "The threat is extremely concrete, and there is no choice but to do everything possible," a source involved in aviation security...