You may apply to extend your stay if you were lawfully admitted into the United States with a non-immigrant visa, your non-immigrant visa status remains valid, and you have not committed any crimes that would make you ineligible.

You must apply to extend your status if you wish to stay longer than the date indicated in the lower right-hand corner of your INS Form I-94 (Arrival-Departure Record). You must submit the application for an extension of stay BEFORE your current authorized stay expires. You must also keep your passport valid for your entire stay in the United States.

You may not apply to extend your stay if you were admitted to the United States in the following visa categories:

(VWPP) - Visa Waiver Pilot Program
D - As a crewman
C - As an alien in transit or in transit without a visa
K - As a fiancé of a U.S. citizen or dependent of a fiancé
S - As an informant (and accompanying family) on terrorism or organized crime