Forecasting the air passenger traffic is a vital element in airports functioning. It enables effective usage of infrastructure and available workforce. Therefore, the aim of the paper is to carry out a forecast of the air passenger traffic on the basis of chosen methods. The example for the studies was the Solidarity Szczecin-Goleniów Airport. Data in the monthly and quarterly basis from the years 2010?2016 was used in the analysis. The following forecasting methods were adopted in the paper: seasonality index, Naive Bayes classifier for a time series with seasonal fluctuations and harmonic analysis. The paper finishes with a summary of the obtained results.