Plans to grow the world’s busiest passenger airport have hit a snag, with space and cost constraints forcing planners to change things up.

Hartsfield-Jackson Atlanta International Airport, currently undergoing a $6 billion expansion and modernization project, recently opted to scrap blueprints for a new International Concourse G, according to the Atlanta Journal-Constitution.

At roughly $1.5 billion, the price to build out a whole new concourse steered planners in a different direction.

Nevertheless, the airport’s interim assistant general manager for planing and development, Tom Nissalke, told the paper there’s an “immediate need” to create more domestic gates. (Mayor Keisha Lance Bottoms is in the process of selecting a permanent general manager to run the airport, which could dictate how the plans progress.)

Right now, the airport counts 193 gates total. But if this expansion plan is going to accommodate the city’s fast-growing population, airport officials will need to squeeze more gates onto existing concourses, which are being extended, the AJC reports.

Construction is already underway on multiple aspects of the airport’s growth, such as the extension of Concourse T, which will add five new gates to its northern side.

Hartsfield-Jackson officials are also conducting an environmental study—mandated by federal law—which will determine how to proceed with gate development and the rebuild of domestic terminal parking decks erected in the 1970s.

That assessment could be completed early 2019, and project officials are also weighing the possibility of creating new parking decks that could one day be converted to office space, should Atlanta’s love affair with automobiles fade.

The airport is also debating whether to extend Concourse T to the south with six to eight more gates jutting out to the west, or growing Concourses B, C, and D with two gates each, AJC reports.

Either way, the airport would be looking at a bill between $400 and $500 million.

Of course, all the upcoming construction won’t be easy on the airport. Building new gates will require a lot of moving, major parts.

More gates on Concourses B, C, and D would mean two taxiways would need to shift. A south side extension to Concourse T would call for an adjustment to the cell phone lot, among other changes.

Elsewhere in Hapeville and other airport-area neighborhoods, Aerotropolis project planners are conducting a study to determine how certain transit systems could help move people to and from airport neighborhoods.