Ukrainian boxing champion Oleksandr Usyk was handcuffed at a Polish airport after he became "upset" when his travelling companion was denied boarding for disruptive behaviour, the airline and border guards said Wednesday. World heavyweight champion Usyk described the incident late Tuesday as a "misunderstanding" while Ukrainian President Volodymyr Zelensky said he was "disappointed by this attitude towards our citizen". The 37-year-old boxer had been planning to fly from Krakow airport to Thessaloniki in Greece along with another man on a flight Tuesday operated by Polish airline Buzz, a subsidiary of Ryanair.