Switzerland has agreed to let United States planes with humanitarian goods use its airspace, however, military planes are not allowed to fly over its territory.
"The approval is for flights for humanitarian purposes alone," said foreign ministry spokeswoman, Muriel Berset Kohen.
Kohen confirmed that the permission does not extend to US planes carrying weapons or people involved in the current fighting in Afghanistan.
Civil aviation authorities granted their approval last weekend, and two US aid flights crossed over Switzerland on Thursday, she added.
Each flight has to be individually given the green light to enter Swiss airspace. No weapons, military supplies or military personnel should be on board.
Further, pilots are required to identify the crew and cargo before being given permission to fly through Switzerland.
A flight planned for last Sunday was forced to take a different route after the pilot had communication problems with the Swiss aviation authorities.
swissinfo with agencies
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