German tourist Erwin Kreuz took a flight from Augsburg to San Francisco. When it landed in the United States, he got off.
Three days later, he realized he wasn't actually in San Francisco. Instead, he was in Bangor, Maine, where the plane had stopped for refueling. Kreuz realized his mistake when he got bored of wandering around what he thought were the suburbs of San Francisco, got in a cab, and asked to go to downtown San Francisco. The cabbie somehow managed to inform him (despite Kreuz's total lack of English) that it would be a very long trip.
Kreuz later explained that when he had been sitting on the flight, after it had landed, a stewardess had walked past him and wished him a "pleasant stay in San Francisco." The crew was being switched during the refueling, so she was just saying goodbye, but Kreuz assumed it meant they had arrived in SF. So he deboarded, went through customs, and managed to get a cab to a local hotel.
When the media got word of Kreuz's mix-up, he became a national celebrity. The SF Examiner flew him out to San Francisco at their expense, where he got to meet the mayor and tour the city.
A year later Kreuz returned to Bangor to be the celebrity guest at the opening of a shopping mall, but things for him then went downhill because the brewery where he worked back in Germany fired him for taking too much time off.
In 1979, Kreuz returned to Bangor a third time, hoping to find a job by cashing in on his celebrity. But the only job he was offered was as a janitor. So he returned to Germany.
More info: Wikipedia
, Bangor Daily News
The La Crosse Tribune - Oct 29, 1977