The grass of a baseball field in Prospect Park shuddered under the blades of a New York Police Department helicopter on Friday afternoon. Dust flew in the air. Soon, Mayor Bill de Blasio clambered aboard.

In a car, it might have taken 30 minutes or longer for him to make the roughly seven-mile drive from his old Brooklyn stamping grounds to an event in Queens.

By air, the trip — a fantasy of nearly every New Yorker ever caught in traffic on the Brooklyn-Queens Expressway — was considerably shorter.

But the headache it caused Mr. de Blasio on Monday might not have been worth the trip, as a photograph and a video of the copter incongruously parked in the middle of a city park ricocheted around the internet, and reporters waited outside City Hall to ask him about it.