CLass C = transit visa
C-1 Visa - General Transit Visa
If a non-US citizen is passing in immediate and continuous transit through the United States, he/she may require a valid transit C-1 visa, unless he/she is a citizen of a country that has an agreement with the United States allowing their citizens to travel to the United States without a visa or they are eligible to transit the United States without any visas under the Visa Waiver Program.
A foreign national can apply for a C2 visa, if he/she is an invitee, accredited representative of an information media company, or a representative of a consulting nongovernmental agency traveling to or from the United Nations headquarters district in New York City.
C-3 Visa - Foreign Government Transit
A member of a foreign government on official business can obtain a C3 visa while transiting through the United States. The official's immediate family members, attendants, servants, or personal employees are also permitted to pass through United States..