So long, Reagan National Airport’s outdoor gates.

The Metropolitan Washington Airports Authority on Wednesday showed expanded plans for its biggest renovation project at National in more than 20 years. The project, called Project Journey, will be a multiyear, $1 billion construction project that will provide a new commuter concourse and two new security checkpoints.

The airport, designed to serve 15 million customers annually, now sees more than 23 million passengers travel through the airport,…