Dynametric tailfins

From Memory Alpha, the free Star Trek reference.

Dynametric tailfins were a creation of Tom Paris designed to add sleekness and a sense of power to the Delta Flyer shuttlecraft.

In 2375, Paris attempted to add the tailfins when plans for the Delta Flyer were being considered. They were removed by Tuvok, who stated that they were not making a "hot rod". (VOY: "Extreme Risk")