Some of the deadliest days for U.S. troops in Afghanistan:

-- Oct. 26, 2009: Eleven American soldiers are killed in separate helicopter crashes. One chopper goes down in western Afghanistan, killing seven soldiers and three civilians working for U.S. government. In a separate incident in the south, two other U.S. choppers collide while in flight, killing four American troops.

-- Oct. 3, 2009: Eight U.S. soldiers are killed when their outpost in Kamdesh, Nuristan, is attacked by as many as 300 militants. Another soldier died in Wardak province when an IED detonated while he attempted to disarm it.

-- July 13, 2008: Nine American soldiers are killed when their remote outpost in Wanat, Nuristan, is attacked by small-arms fire and rocket-propelled grenades. Another soldier died in Kajaki Sofla when his vehicle struck an IED.

-- Feb. 18, 2007: A U.S. helicopter crashes in the Shahjoi district of Zabul province, killing eight American troops. NATO said the pilot had reported engine trouble.

-- May 5, 2006: Ten American soldiers die in a CH-47 Chinook helicopter crash during combat operations in eastern Afghanistan; the U.S.-led coalition says hostile fire was not involved.

-- June 28, 2005: In the deadliest single blow to American forces in Afghanistan, 16 U.S. troops on a special forces helicopter are killed when their MH-47 Chinook helicopter is shot down by insurgents. Three U.S. sailors also die the same day in support of the Afghan mission.

-- April 6, 2005: 15 U.S. service members and three American civilians are killed when their helicopter goes down in a sandstorm while returning to the main U.S. base at Bagram.

-- Jan. 29, 2004: An explosion at a weapons cache in Afghanistan kills eight U.S. soldiers.

-- March 23, 2003: A U.S. Air Force helicopter on a mercy mission to help two injured Afghan children crashes in southeastern Afghanistan, killing all six people aboard.

-- March 4, 2002: Seven American soldiers are killed when two helicopters come under fire.

-- Jan. 9, 2002: A U.S. military refueling plane that was resupplying troops in Afghanistan crashes in Pakistan, killing all seven Marines aboard. According to a military report released in June 2002, human error likely caused the crash.