The Visa Waiver Program (VWP) currently covers more than 40 countries (administered by the U.S. Department of Homeland Security in consultation with the U.S. Department of State) and allows eligible citizens or nationals to travel to the United States for tourism or business for stays of 90 days or less without obtaining a visa. Travelers must (1) be a citizen/national of a VWP country, (2) hold a valid biometric/e-passport, and (3) obtain an approved Electronic System for Travel Authorization (ESTA) before departing for the U.S.
U.S. visitor visa applicants typically must submit the DS-160 form, pay the required application fee, and appear for an in-person interview at a U.S. Embassy or Consulate. U.S. immigration policy in 2025 also includes additional security screening, and certain visa categories may be subject to new supplemental fees. Please contact your local U.S. consulate or embassy for up-to-date information.
Invitation Letters
If you require a personal letter of invitation to attend DASC 2026, contact the Conference Manager. In your email, provide the following information:
Mailing address
Nationality
Date of Birth (if required by your embassy/consulate)
Accepted paper number (if applicable)
Accepted paper title (if applicable)
Any other details that your country of residence requires for your visa application
The letter will be provided by email ONLY. DASC 2026 cannot contact or intervene with any Embassy or Consulate office on your behalf so please begin your visa application process as soon as you determine that you want to attend DASC 2026. Begin your visa process as early as possible (many posts have long interview wait times) Please provide complete information as possible to avoid delays in receiving your letter. You must register for the conference and pay in full before requesting an invitation letter. Many U.S. Embassies require proof of conference participation (such as acceptance of a paper or proof of registration). Some consulates will not issue a visa support letter until you have completed and paid your registration; please confirm your consulate’s requirements.
The Visa Waiver Program
The VWP allows eligible citizens of designated countries to visit the United States for business or tourism for up to 90 days without first obtaining a B-1/B-2 visa, provided they have an approved ESTA. The program is managed by the U.S. Department of Homeland Security in consultation with the U.S. Department of State. The number of participating countries is now over 40.
The program was established to eliminate unnecessary barriers to travel, stimulating the tourism industry, and permitting the Department of State to focus consular resources in other areas. VWP eligible travelers may apply for a visa, if they prefer to do so. Nationals of VWP countries must meet eligibility requirements to travel without a visa on VWP, and therefore, some travelers from VWP countries are not eligible to use the program.
Electronic System for Travel Authorization (ESTA) approval is required before boarding any carrier to the U.S. (air or sea) and is now also required for VWP travelers entering by land. ESTA approvals are generally valid for two years or until the passport expires, whichever comes first, and allow multiple short visits. You cannot extend your stay beyond 90 days or change to another immigration status once in the U.S. under VWP.
VWP travelers are required to have a valid authorization through the Electronic System for Travel Authorization (ESTA) prior to travel, are screened at the port of entry into the United States, and are enrolled in the Department of Homeland Security’s US-VISIT program.
Eligibility for admission under the Visa Waiver Program
Nationals of the 40 countries participating in the Visa Waiver Program may use VWP if:
They have received an authorization to travel under the VWP through the Electronic System for Travel Authorization (ESTA). ESTA should be obtained at least 72 hours before travel;
Travelers using VWP must present an individual, valid, machine-readable biometric/e-passport (an e-passport with a digital chip). U.S. law generally requires your passport to be valid for at least six months beyond your intended stay; however, the U.S. has agreements with many countries (including most VWP countries) that waive the extra six-month requirement and instead require validity only through your intended departure date. Check your country’s rules before travel;
The purpose of their stay in the United States is 90 days or less for tourism or business (visitor B-1/B-2 activities). If in doubt, travelers should check with the nearest U.S. Embassy or Consulate to verify that what they plan to do is considered tourism or business. Transit through the United States is generally permitted;
VWP travelers arriving by air or sea must arrive via a carrier approved by U.S. Customs and Border Protection and must have a return or onward ticket showing departure within 90 days. Travelers entering by land from Canada or Mexico must also have an approved ESTA as of 2022, though the “approved carrier” requirement applies to air/sea only;
They can demonstrate the intent to stay 90 days or less in the United States and demonstrate sufficient funds to support themselves while in the United States. Learn more on the CBP website;
VWP travelers who have been admitted under the Visa Waiver Program and who make a short trip to Canada, Mexico, or an adjacent island generally can be readmitted to the United States under the VWP for the balance of their original admission period. For additional details, see the Department of Homeland Security’s Customs and Border Protection (CBP) website. Also, VWP nationals resident in Mexico, Canada, or adjacent islands are generally exempted from requirements to show onward travel to other foreign destinations.