The A-1 visa is a non-immigrant visa which allows travel to United States for ambassadors, ministers, diplomats, consular officers, and their immediate family members. While government officials normally do not qualify for an A-1 visa if they are traveling for non-official, non-governmental purposes, heads of state always qualify and must apply for an A visa regardless of their purpose of travel. Visitors on an A-1 visa cannot be tried under US law for a crime, and may travel to and from the country an unlimited number of times. There is no maximum length of stay for individuals admitted on an A-1 visa, and there is no requirement to maintain a foreign residence.
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A-1 visa Wikipedia(Text) CC BY-SA