NATO says a rocket or mortar attack at Bagram Air Field damaged the plane that was used by the chairman of the U.S. Joint Chiefs of Staff, General Martin Dempsey, who was making a visit to Afghanistan.
The International Security Assistance Force says "shrapnel from an indirect fire round" struck the door of the C-17 transport plane that brought Dempsey to Afghanistan. He left later on August 21 in another C-17 transport plane.
ISAF spokesman Brigadier General Guenter Katz told RFE/RL's Radio Free Afghanistan that the projectile was one of "two rounds" that struck Bagram overnight while Dempsey's plane was there.
"Two rounds impacted at Bagram Airfield last night and the shrapnel of one of those rounds damaged an ISAF helicopter and damaged the C-17 of General Dempsey, who was visiting Afghanistan. During that time, however, General Dempsey was already in his room, and he was not on the ramp any more," Katz said.
Katz told RFE/RL he is unable to confirm whether the round was a mortar or a rocket.
Indirect fire means the weapon's trajectory has a high arch, like a rocket that is fired from a long distance or a mortar round. They contrast direct fire weapons that have a relatively flat trajectory -- such as rifles and machine guns, anti-tank guns and anti-tank rockets.
Taliban fighters are known to have supplies of Russian-built Sakar-20 rockets and have used them for indirect fire attacks against U.S. and NATO troops along Afghanistan's eastern border with Pakistan.
The Taliban has claimed responsibility for the attack, saying militants had received inside information about the exact location of Dempsey's plane.
But NATO officials say the militants are not known to have the ability to accurately strike targets at Bagram, which is where foreign dignitaries usually arrive for visits to Afghanistan.
NATO maintains the shrapnel that hit Dempsey's plane was probably the result of a lucky shot.
Dempsey was in Kabul on August 20 to discuss a growing number of so-called "insider attacks" by Afghan government troops against U.S. and NATO soldiers.
He said after his talks with Afghan military leaders that his Afghan counterparts are "for the first time" as concerned as Washington about the issue.
Insider attacks have killed 10 U.S. soldiers since the beginning of August.
The total death toll from insider attacks this year has already reached 40, which makes up 13 percent of all international coalition deaths so far in 2012.
With reporting by AFP, AP, and Reuters