If you arrived in the United States on a business (B1) or tourist (B2) visa and wish to extend your stay beyond the initially allowed period, you need to apply for an extension with Form I-539. This extension is crucial to maintaining lawful status, which is necessary to avoid deportation and qualify for future immigration benefits. Ensure you meet all eligibility criteria, including maintaining lawful behavior and continuing the same activities for which you were originally admitted. Applying on time is essential, though exceptions may apply for extraordinary circumstances.