It is all above board, however, as Dubra's work of art is part of the ongoing Vilnius Street Art festival, which is taking place in Lithuania's capital city for the third successive year.
Indeed, the airport went out of its way to ensure that 26 metre high tower was made available as a location for Dubra, who is Lithuania's sole artist in the festival, which aims to change the public's perception and attitudes to street art.
"We wish to create as good impression of Vilnius before passengers even leave their planes," says Indrė Baltrušaitienė, head of communications & marketing at Lithuanian Airports.
Baltrušaitienė notes that the gateway chose the water tower as the artwork can be seen from aircraft taxiing to the terminal.
According to the festival organisers, Antanas Dubra is arguably the most famous street artist in Vilnius, adding that the city would be different without his wall paintings.
Dubra calls his artwork at the airport 'The grumpy side of the moon'.