Application to Extend or Change Nonimmigrant Status Form I-539 The "Application to Extend or Change Nonimmigrant Status" refers to Form I-539 in the United States, which is used by individuals in certain non-immigrant visa categories to request an extension of their stay or a change to a different non-immigrant status. This form is commonly used by individuals who want to prolong their stay or switch to a different visa category while remaining in the U.S.