<p>I think it’s the first (“A fleet of vehicles is being made”), but the second sounds nicer to my ear. Which is correct?</p>
<p>Is. </p>
<p>Fleet is singular.</p>
<p>its not the vehicles we are talking about its the fleet… so there is one fleet and is singular… dont go by your ears its misleading most of the times</p>
<p>ditto. “is” is correct</p>
<p>“[O]f vehicles” is a prepositional phrase. The subject is “fleet,” which is singular.</p>