This from the US embassy website
On August 2, 2003 the Department of Homeland Security announced the indefinite suspension of the Transit without a Visa Program (TWOV) program and the International-to-International Transit Program (ITI), pending a review within the next 60 days. This announcement does not affect qualified travelers traveling visa free under the Visa Waiver Program.
To minimize inconvenience to travelers, those who were seeking to transit the United States under TWOV or ITI who purchased their tickets as TWOV or ITI passengers on or before July 24, 2003 and who are scheduled to depart for transit through the United States before 12.01 a.m. EST, Tuesday, August 5, 2003 may still transit without a visa, provided they are otherwise qualified. Travelers with tickets purchased after July 24 or those with tickets purchased on or before that date, but not scheduled to depart in transit until after 12.01 EST, Tuesday, August 5, 2003 will either be required to apply for a U.S. visa, or change their travel itinerary to exclude a stop in the United States.
Travelers who have already made the outward journey through the United States under the TWOV or ITI programs and are seeking to transit the United States on the return journey must use the return portion of their round trip ticket before 11:00 a.m. EST, August 9, 2003. Travelers who are not on their return journey through the United States or those whose return journey will take them through the United States after 11:00 a.m. EST, August 9, 2003 will either be required to apply for a visa, or change their travel itinerary to exclude a stop in the United States.
Important Notice: The suspension of the TWOV program does not affect visa free travel under the Visa Waiver Program. Qualified visa free travelers may continue to travel to the United States for business or pleasure or in transit through the United States
