Grand Central is poppin’. 

A series of mysterious giant balloons have been floating above the daily frenzy of rushing commuters and wide-eyed tourists in the station’s iconic Main Concourse for months – spurring many passersby to do a double take. 

The inflatables have included a bright red heart-shaped balloon; a star emblazoned with “USA” and another in the shape of the No. 3, as some visitors are left wondering if they were released intentionally in a social media stunt or for some other unknown reason.

The puzzling installation 125 feet up has sparked plenty of hot air among travelers, whose reactions have ranged from amused to annoyed to simply blown away. 

“Whatever is going around, someone needs to look up there – and it gives you a lot of hope,” said a Queens resident who stopped to take a photo of the heart-shaped balloon. 

“I love it. I think we all need a lot of love right now,” said the woman, who only gave the name Bhumika. 

Eve Shafer, a 16-year-old tourist from Westport, Connecticut, noted that the balloons “change the aesthetic but don’t ruin it.” 

“I think it’s really pretty and I feel like it’s kind of like accidental art in Grand Central,” Shafer told The Post. 

Additionally, “I think it’s really cool that it’s been here for so long,” she continued, referring to the heart-shaped balloon, which has been a mainstay inside the terminal for months. 

Jessica Van Der Hoorn, a Netherlands native, said she’d seen the heart-shaped balloon featured in social media videos before coming to the station – and guessed that it ended up on the picturesque ceiling as an accident. 

“I think it’s more of a little child with a balloon, it slipped out of her hands and it’s now stuck on the ceiling. That’s what I pictured,” she said. 

Van Der Hoorn was correct: all of the balloons seen in the terminal so far this year, including the popular heart-shaped one, have been the result of “accidents,” according to a Grand Central Station engineer. 

“The heart has been up there since about a week before Valentine’s Day and, of course, we can’t take them down,” the worker told The Post. 

The engineer, who declined to give his name, said workers were actively trying to figure out a way to get high enough to reach the balloons – and get rid of them without jeopardizing the architecture. 

“There’s no way of getting up there. 

“We’re in the process of trying to get a drone, put a little pin on the front so we can fly it up there and kind of pop them…but you can’t damage the ceiling,” the worker explained. 

“It’s a national landmark, so we have to preserve it. We have to follow a big, big book of rules,” he continued. 

For now, they’re letting chemistry do the work for them.  

“We usually just wait for the helium to lose its effect…the big one’s going to take a while. The little one, maybe another week or so,” the employee said. 

Accidents or not, many station visitors expressed equal concern for the landmark’s integrity – and slammed the balloon-releasers as uncivilized.

“Me and my friends were just talking about it, that it’s a little disrespectful, maybe, to let them go on the ceiling, because it’s such a nice piece of architecture,” said 15-year-old Emily Heit, who lives in the Floral Park neighborhood of Long Island. 

“If people are coming to New York to see this station, because it’s really pretty, it’s just kind of rude and in the way of the art form, I’d say,” agreed Victoria Ambrose, also 15, who traveled into the city with Heit and their ground of friends.

Juan Esteban Gil, a World Cup attendee from Colombia, worried that the balloons “must somehow damage the aesthetic of this emblematic place.”

“But I don’t know, it’s whatever New Yorkers like,” he concluded. 

The Metropolitan Transportation Authority, which oversees the station, said in a statement that main floor staff “remind customers bringing balloons into the terminal to handle them carefully.”