three types of O visas O-1, O-2, and O-3

O-1 foreign nationals for `extraordinary ability`

O-2 aliens accompanying and assisting O-1 artists and athletics

O-3 a spouse and any unmarried minor children of the O-1 and O-2 aliens.

This category of visa covers foreign national with “extraordinary ability” in the sciences, arts, education, business or athletes as demonstrated by sustained national or international acclaim. Extraordinary ability is defined as “a level of expertise indicating that the individual is one of the small percentages who have risen to the top in the field of endeavor”. This category also includes aliens of `extraordinary achievement` in the motion picture or television industries. The petition for O-1 visa is valid for the period of time necessary to accomplish the event or activity not to exceed three years. However, to accomplish the event or activity for which he or she was admitted. The alien is not required to demonstrate that he or she maintains a foreign residence. If the alien is dismissed, the employer must pay the reasonable cost of the alien`s transportation abroad.

SPECIAL RULES FOR CANADIAN AND MEXICAN RESIDENTS

NAFTA established four categories of nonimmigrant visas to facilitate the entry of Canadian and Mexican citizens into the United States

1) business visitors

2) intracompany transfers

3) professionals

4) investors and traders

These categories are in addition to the existing nonimmigrant categories available to citizens of other countries. Mexicans and other Canadian citizens who do not qualify under any of the NAFTA categories may still qualify for temporary entry under the existing classifications. CIS regulations permit Canadian citizens to apply for the TN visa from an immigration officer at a U.S. Class A port of entry, a U.S airport handling international traffic, or a U.S. preclearance/preflight station. No prior petition or CIS approval is required.

Mexican citizens, on the other hand, must file an LCA.