The NATO-1 visa is a non-immigrant visa which allows representatives from NATO member states, their official staff, and their immediate family members to travel to United States. Recipients are normally exempt from inspection, and the visa is valid for the duration of the individual's stay in the US. Heads of state traveling to the US are ineligible for this visa category, even when on official NATO business, and must apply for an A-1 visa regardless of their purpose of travel. NATO officials and their family members may not utilize the NATO-1 visa if traveling for a purpose other than official business, and must instead apply for the alternate applicable visa category.
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NATO-1 visa Wikipedia(Text) CC BY-SA