Invitation Letter

International participants arriving from outside the United States who hold a passport from 1 of the 36 countries in the Visa Waiver Program have a machine-readable passport may be able to travel without a visa. Participants from other countries will need a B-1 (business) visa or B-2 (tourist) visa.

Obtaining a U.S. visa may require a visit to a U.S. consulate or embassy, payment of a fee, and significant wait time. The information on this page is provided as a courtesy, and is subject to change. Please contact your local U.S. consulate or embassy for up-to-date information.

Invitation Letters

You must register for the conference and pay in full before requesting an invitation letter.

The letter will be provided by email ONLY and after a successful paid registration has been received. The Symposium cannot contact or intervene with any Embassy or Consulate office abroad on your behalf so please begin your visa application process as soon as you determine that you want to attend SPCE 2024. Please provide as much information as possible to avoid delays in receiving your letter. 

The Visa Waiver Program

The Visa Waiver Program (VWP) enables nationals of 36 participating countries to travel to the United States for tourism or business (visitor [B] visa purposes only) for stays of 90 days or less without obtaining a visa. 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. 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

  • Review this VWP-Quick Reference Guide (for new member countries) and make sure you review this webpage for detailed information. Nationals of the 36 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)
  • They present the appropriate type of passport valid for six months past their expected stay in the United States This is a requirement in addition to other passport requirements for all categories of passports -- regular, diplomatic, and official - when the traveler is seeking to enter the United States for business or tourist purposes, for a maximum of 90 days;
  • The purpose of their stay in the United States is 90 days or less for tourism or business (Visitor (B) visa) purpose of travel. (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.
  • If arriving by air or sea, they are traveling on an approved carrier and have a return trip ticket to any foreign destination;
  • 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. Learn more at the  CBP website.