The Visa Waiver Program comprises tourists and business visitors. Eligibility for this category is limited to foreign nationals from certain countries (mostly Europeans). Foreign nationals may visit the US for up to 90 days, but they may usually not extend their stay in the US or transfer to a different nonimmigrant (temporary) or immigrant (permanent) status without first departing the US. As with B-1 business visitors and B-2 tourists, they may not be on a US payroll.