The daily flight AY666 from Copenhagen to Helsinki falls on Friday 13 twice in 2013, and today's flight is nearly full.
AY666 falling on Friday 13 has long been a joke among Finnair pilots. Veteran pilot Juha-Pekka Keidasto, who will fly the route from Copenhagen to Helsinki today, says "I'm not a superstitious man. It's only a coincidence for me."
Friday 13 is considered bad luck in some cultures, and the number 666 has strong negative associations in Christianity, sometimes referred to as "the number of the beast."
As a result, some airlines go so far as to omit the 13th row from their planes. Scandinavian Airlines has done this, even though superstition over the famous date is relatively new to the region.
"Less than 100 years ago, the number 13 did not have this sinister meaning; it's quite recent in the north," said Ulo Valk, professor of comparative folklore at the University of Tartu in Estonia.
"There are 12 hours, 12 months and in Christianity 12 apostles and this is a divine number. Add one more and it brings in a certain element of chaos," Valk speculated.