He estimated that the Adriatic Express could carry up to 11,000 passengers by the end of August.
Ninety percent of the available seats were sold for the train's maiden voyage, Klimczak wrote on X.
"It is not only a fast and convenient connection, but also a symbol of accessible, European holidays, from smaller towns as well," he added. He noted that in Poland the train stops in Opoczno, Włoszczowa, Sosnowiec and Katowice, among other stations.
The Adriatic Express will run throughout the summer - and its premiere run started on Friday at around 2 p.m. in Warsaw.
After leaving Poland, the Adriatic Express passed through the Czech Republic, Austria and Slovenia, to finally reach Rijeka in Croatia.
The train will run four times a week in each direction. Its route is approximately 1,240 kilometers long and is among the longest in Europe.
The first return journey of the new train to Poland began at 6:15 p.m. on Saturday and ended at 2:16 p.m. on Sunday at the Warszawa Wschodnia (Warsaw East) station.
The Adriatic Express will run until the end of the summer holidays. The last departure from Warsaw will take place on August 28, and from Rijeka on August 29.
PKP Intercity is the largest Polish rail operator, providing transportation between large cities and popular tourist resorts in the country, as well as enabling travel around Europe.
PKP Intercity trains carried 78.5 million passengers last year, 15 percent more than in 2023 and 33 percent more than in 2022.
The carrier aims to handle 88 million passengers this year, followed by 110 million in 2030.
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Source: PAP, IAR
Click on the audio player above for a report by Michał Owczarek.