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Downsview Airport, in northwest Toronto, has undergone a few transformations in its time. About 100 years ago, the first airfield was built: a short runway and an industrial building among farmers’ fields. It was the site of De Havilland Canada, a pioneering global aviation company.
It became a hub of warplane production during World War II, and in the early 1990s, the airfield was acquired by Bombardier, a Canadian aerospace manufacturer. In 2024, it was shuttered, as the firm relocated.
But in early 2026, construction begins on what will be the site’s biggest evolution yet. The 370-acre area is being developed into an urban district housing more than 50,000 residents and 75 acres of green and open space. It will become “YZD” –– a nod to the former airport call sign –– a 30-year, $30-billion development and one of the largest projects of its kind in North America.
The 2-kilometer (1.24-mile)-long runway, the site’s centerpiece, will become a pedestrianized park that links seven neighborhoods. Each one will be distinct, with its own housing, libraries, shops, schools and community centers, but the airstrip will act as the “connective tissue” — tying it all together while “respecting and celebrating the aerospace legacy of the site,” said Derek Goring, CEO of Northcrest Developments, the firm leading the project.
He told CNN that maintaining the history of the site was a key part of Northcrest’s vision — and also a huge advantage. “One of the biggest challenges with large-scale urban redevelopments is when you don’t have anything to start with, they can feel generic,” he said. “We want to lean into what’s there and make as much use of it as possible. It helps bring character and it makes it more interesting and unique.”
A greener future
Preserving the site’s history is not just a sentimental decision, it’s a practical one in terms of its environmental footprint.
“There’s a lot of embedded carbon in the existing buildings and rather than tearing them down and building everything new, there’s a big carbon benefit to retaining those buildings,” said Goring.
In photos: the second lives of former airports
The vast, industrial airport hangars, built between the 1950s and 1990s, will be maintained and repurposed into commercial buildings, serving film production, light manufacturing and clean tech. Their roofs will be covered in grass and plants, which the developer claims will help to absorb rainwater and reduce the risk of flooding, while enhancing biodiversity within the urban center.
While the runway will not be retained in its current form, the concrete and asphalt it’s made from can be reused as aggregate for roads or pavements, said Goring. Some other airports and military bases across Canada have been found to contain “forever chemicals” that could contaminate groundwater. The developers said that while a small part of the YZD site “reflects its historic industrial and military past” they have hired specialized environmental consultants who will “help us understand and mitigate any legacy conditions,” and they will continue to review the site in collaboration with local authorities.
Landscape architecture firm Michael van Valkenburgh Associates (MVVA) is tasked with creating a design concept for the runway, after winning an international competition for the project in October. Its goal is to bring nature back into the space.
Emily Mueller De Celis, partner at MVVA, harks back to the history of the site before it was an airfield, or agricultural land, and when it would have been part of the Carolinian forest in southern Ontario. They want to recreate native habitats and invite wildlife back into the site.
“The nature within the existing site had to be suppressed so that it was safe for aviation operations,” she explained, which meant deterring nesting birds despite its location along the Atlantic Flyway, a major migratory route.
“Re-naturalizing” the site will have big benefits in terms of water management too, she said. The YZD site is located at the high point of Toronto, between major watersheds. Through the design, MVVA wants to find ways of absorbing as much water as possible so that it reduces flood risk downstream. This will be done through strategic planting and the use of bioswales (vegetated channels that collect, filter and absorb stormwater).
Environmental sustainability feeds into Northcrest’s bigger picture. The huge development will take three decades to complete, so it needs to be forward-thinking and prepare for more extreme weather and the potential effects of climate change, said Goring.
He added that Northcrest has been working with Danish landscape designers SLA — famed for their work on projects such as Copenhagen’s waste-to-energy plant turned ski slope — on the concept of “City Nature,” which is about creating lots of green space in urban environments to improve quality of life.
The YZD site is already surrounded by a network of train stations and subways, so the design will make use of these and encourage pedestrianization and car-free alternatives. There will be wide cycle lanes and a last-mile bus system.
“It doesn’t mean there won’t be cars — the runway is really the only car-free area,” said Goring, “But we’re trying to (make) walking and cycling the easiest, safest and most convenient ways to get around.”
Legacy
Repurposing abandoned airfields into green parks and sustainable living areas has become something of a global trend, with examples such as Tempelhofer Feld in Berlin and the Ellinikon Metropolitan Park in Athens.
YZD is different, claims Goring. “The fact that our site sits at the geographic center of the largest metro area in Canada, with existing public transit infrastructure, means that it’s more of a city-building exercise than a park,” he said.
Construction of the first neighborhood, the 100-acre “Hangar District,” including 3,000 new homes, will begin early next year — with completion earmarked for 2031. It will be the first phase of a 30-year transformation, with the districts built one by one and the runway slowly evolving between them all.
One of the biggest challenges of the project is its sheer scale and the time it will take to build. Goring says they do not have $30 billion on tap, which is why they intend to build in phases, making an investment, getting a return, and re-investing.
Over such a long development period he expects current ideas and designs to evolve. The goal is not to be overly prescriptive from the get-go: “The world’s going to change a lot … (we’re not) trying to decide in 2025 what the future should be 20 or 30 years from now,” he said.
“Ultimately, it’s about delivering a really high quality of life,” he added, and merging into the current city. “We want it to feel like a part of Toronto.”