In many countries in the Western world number 13 is associated with bad luck. The phenomenon has even been given its own name, triskaidekaphobia, the fear of number 13. There are many possible reasons behind this but one stems from Christianity and the Bible and the Last Supper of Jesus before the cruxifition, of which they were 13 at the table.
Nowadays many companies in the transportation and hospitality tend to avoid number 13. There may not be a room 13 or a level 13 at the hotel for example.
Also some airlines seem to do this, avoiding a row 13, whilst others do not.
Here are some European airlines that do not have row 13 onboard:
Lufthansa, Air France, KLM, Brussels Airlines, Austrian Airlines, SAS, Alitalia, Iberia, Turkish Airlines, Swiss
And here are some that do:
British Airways, Finnair, LOT, Norwegian, Aeroflot, TAP Portugal, Czech Airlines, Air Serbia
In Italy number 17 is considered unlucky, therefore if you travel on Alitalia there will neither be a row 13, nor a row 17.
Would you have a problem with being assigned a seat on row 13?