The 1997 Israeli helicopter disaster, occurring on February 4, 1997, left 73 IDF soldiers dead after 2 Sikorsky CH-53 collided over Moshav Sha'ar Yishuv in Northern Israel. The helicopters were supposed to have crossed the border into Israel's "security zone" in Lebanon, but they were hovering while waiting for official clearance to go. Previously Israel had moved troops by ground, but this policy was changed as the threat of roadside bombs from Hizbullah increased.Eisenberg, Laura Zittrain. http://meria.biu.ac.il/journal/1997/issue3/jv1n3a3.html "Israel's Lebanon Policy", Middle East Review of International Affairs, September 1997.