A subway-obsessed thief infamous for his transit-related crimes was busted in Brooklyn Wednesday for stealing a Greyhound bus from the Port Authority depot, police sources said.

“I’m stealing a plane next,” Darius McCollum, 50, allegedly told detectives who took him in for questioning after he was found with the stolen bus at the corner of Third Avenue and Union Street in Gowanus.

Two cops from the 78th Precinct were on patrol at about 4 p.m. when they received a city-wide radio message alerting them that the bus had been stolen.

They then saw a bus barreling north on Third Avenue and pulled over the empty vehicle, which had plate numbers matching the ones they’d been given, sources said.

The driver turned out to be McCollum, who has been arrested 29 times for various transit-related offenses, sources said.

Charges against McCollum, who was wearing a badge on his shirt when he was apprehended, were still pending as of early Wednesday evening.

The bus arrived at the Port Authority Bus Terminal from Philadelphia at 11 a.m. and was due to head out for Richmond, Va., at 2:15 p.m. Greyhound realized it was missing at about 1:30 p.m. and alerted the MTA, which called the cops, police said.

McCollum’s lifelong love for city transit systems started when he was a youngster growing up in Queens, where he befriended a subway motorman who let him hang out in the crew room at 179th Street F-train terminal.

His rap sheet dates all the way back to the 1980s when he was busted at the age of 15 for driving a passenger-filled E train from 34th St.-Penn Station to the World Trade Center.

Since then, he has impersonated a subway worker, driven a bus from a Harlem depot to Queens Village and gotten behind the wheel of a subway repair truck.

In 2010, McCollum was ­arrested for swiping a Trailways bus from a depot in Hoboken, NJ. He was caught on his way to JFK Airport.

McCollum served just over three years for the crime after taking a plea deal, which allowed him to enter a cognitive-behavioral-therapy program.

His lawyers have said his repeated arrests stem in part from Asperger’s syndrome, an autism-spectrum disorder.

McCollum’s parole prohibited him from operating “any motor vehicle,” but ended this past Aug. 24.

“By curiosity, I was wondering if there are any people out there who may like trains or are even just train buffs,” he wrote on his Facebook page in September. “It’s a passion of mine.”

Additional reporting by Philip Messing and Kathleeen Culliton