It has been more than seven months since the new U.S. Electronic System for Travel Authorization (ESTA) has been mandatory for airlines that fly citizens of visa-waiver countries to the United States. Yet some carriers’ computer systems are reportedly experiencing serious problems, resulting in denied boarding for travelers with valid ESTAs.

Last week, I received a disturbing e-mail message from an Austrian citizen who had read my previous coverage of ESTA issues. On July 5, she wasn’t allowed on a Scandinavian Airlines (SAS) flight from Stockholm to Chicago, for which the carrier blamed problems with the passenger’s ESTA…