With the combat roles of U.S. troops in Afghanistan tapering off, aircraft accidents emerged as the biggest killer of U.S. troops there during the first four months of the year. Since Jan. 1, 13 service members have been killed in five crashes. U.S. troop deaths remain at their lowest levels in Afghanistan in recent years. The number so far this year, 33 through Tuesday, is the lowest at this point since 2008. The next biggest cause of death was improvised bombs, which killed at least eight service members. Four died from causes unrelated to combat. In all, 42 members of the international coalition have been killed in Afghanistan this year, including three whose deaths in an explosion were announced Tuesday.

McClatchy News service