City officials broke ground on a $1.2 billion project that will grow the 1990s-era Terminal 5 complex by 350,000 square feet by adding ten new gates, passengers amenities, security lanes, and an upgraded baggage handling system.

“Chicago and its airline partners are propelling the nation’s best-connected travel hub to the next level, starting with a more than $1 billion infusion that will bring new gates and expanded amenities to Terminal 5,” said Mayor Rahm Emanuel in a statement. “With the improvements, we are making today, O’Hare will continue to set new records and fuel more connectivity, tourism, and economic impact for the city well into the future.”

The angular design comes from Chicago architecture firm Muller & Muller and is expected to be completed in 2021. Later phases of the Terminal 5 project call for a new parking garage, pedestrian bridge, and curbside improvements. A new terminal-adjacent hotel is also under consideration, according to the Chicago Department of Aviation.

A revamped Terminal 5 is part of the larger $8.5 billion “O’Hare 21” modernization effort, which kicked off in 2017 with a five-gate addition to Terminal 3. The centerpiece of the ambitious plan will be the upcoming O’Hare Global Terminal, slated to replace Terminal 2 in 2028. While five teams of architects are currently vying to design the massive building, it’s unclear when the city will announce the winning proposal. A choice is expected to be made before Emanuel departs office in May.

This past year, O’Hare International Airport reclaimed top spot as the nation’s busiest airport by operating more than 900,000 flights for the first time since 2007. Wednesday’s Terminal 5 groundbreaking coincided with an announcement that Israel’s EL AL airline will start offering nonstop flights between O’Hare and Tel Aviv in March 2020.