If you are planning to travel to Alaska, please visit the U.S. Electronic System for Travel Authorization (ESTA) website at least 72 HOURS in advance of departure to complete the new online requirements for visitors from the Visa Waiver Countries (ie. EU, Japan, etc.). This system replaces the traditional I-94 paper application previously done on board.
Application Webpage: Electronic System for Travel Authorization (ESTA)
For detailed information on the rules and help with the application process, visit this link:
Help Webpage: U.S. ESTA Help and Information
**Effective January 20, 2010, all visitors to the U.S. from visa waiver countries MUST complete the ESTA requirements at their website at least 72 HOURS PRIOR to flying.**
Here is another helpful article about the ESTA requirements and new enforcement of the policy.