The NYPD used a multimillion-dollar counterterrorism plane to shuttle Mayor Bill de Blasio back and forth from his Canada vacation to the Big Apple for an event Thursday, The Post has learned.

Hizzoner, who is in Quebec on a weeklong respite, briefly flew back to the Bronx for a memorial for slain Detective Miosotis Familia.

“NYPD is transporting him in their plane,” de Blasio spokesman Eric Phillips told The Post.

“Their plane” is a Cessna 208 Caravan that cost roughly $3 million and was picked up by the department in 2017, sources said.

The high-tech aircraft is outfitted with special sensors that can detect at a distance radioactive material used to make “dirty bombs.”

Police sources questioned the use of a special plane for mayoral transportation.

“It is very unusual to go on an international flight to go pick up the mayor,” one source said.

“I think it’s excessive, because that wasn’t what that plane was designed to do. It’s designed for counterterrorism measures. To go to Canada to get the mayor? It’s excessive.”

Sources said the aircraft is kept at MacArthur Airport on Long Island. Data from flight-tracker website FlightAware shows a Cessna Caravan with a tail number previously identified by Wired.com as belonging to an NYPD “spy” craft flying from MacArthur at 6:36 a.m. Thursday and landing at Montreal-Trudeau Airport by 8:18 a.m.

The plane departed Montreal less than an hour later and landed at Westchester County Airport near White Plains at 10:58 a.m.

By noon, the mayor was speaking at a street co-naming for Familia. The plane later departed Westchester for Montreal at 1:48 p.m., arriving at 3:34 p.m., records show.

The trip to Canada was a departure from the plane’s normal pattern of two- to three-hour flights starting and ending at MacArthur, data shows.

Phillips said that Thursday was the first time the mayor had been on the plane.

Neither the NYPD nor the Mayor’s Office would say who decided to use the plane, how much the trip cost taxpayers or why the mayor didn’t take a commercial flight — which is about $300 round-trip.

A source said the cost of using the Cessna would be in the thousands.

“The NYPD, as a longstanding matter of policy, does not comment on specific details regarding the protection of elected officials,” a spokesman said.

“However, careful consideration is made to ensure that the work of the security detail has no impact on other NYPD operations.”

De Blasio is expected to return from vacation on Sunday.