Go through your results for flights to Mariehamn in Finland with Netflights. The most popular airlines for this route are Finnair, with Finnair claiming the top spot. Although Finnair usually has the best prices, it's best to double check what's available for your travel dates.
Flexible on dates? Conducting your search by month allows you to compare prices to Mariehamn throughout the year. Accommodation prices will also be higher at this time of year.
Mariehamn receives two direct and indirect flights every week, but the cheapest airline is normally Finnair. So, if the flights to Mariehamn don't work for you, you could always try searching for flights to other airports in Finland.
For even more options, check what other airports you could fly to Mariehamn from. You might be able to make a saving by going from a different airport or city.