Already some preliminary work has begun on a $1 billion construction project at Reagan National Airport, but there’s still lots of work to be done before a new commuter concourse is completed by 2021. This spring, demolition is expected to begin on the airport’s executive offices.

Once the project is complete, there will be a concourse for short-hop flights, which will replace Gate 35X. The Washington Post reported that Gate 35X is infamous for being a “choke point” for travelers who are required to board shuttle buses to get to their planes.

The glass-enclosed walkway on the concourse level of Terminals B and C, known as National Hall, will also experience changes that are expected to complete by the fall of 2020. These changes involve moving security screening to the upper level arrival level.

According to The Washington Post, this will be the first major construction project at National Airport since Concourses B and C were opened in the late 1990s.