Updated

Atlanta's airport is embarking on a major project to extend the tunnel for the "plane train," which carries passengers between terminals, to the ground transportation area.

Hartsfield-Jackson Atlanta International Airport officials say they're planning an informational meeting on Sept. 20 to discuss details of the project, one part of a $6 billion capital improvement project at the world's busiest airport.

Airport officials said in a statement that the plane train project will extend the train west from its current endpoint beneath the domestic terminal. It will involve construction of a 600-foot tunnel, plus evacuation stairways and other equipment.

In March, airport officials announced $6 billion in upgrades during the next 20 years. Among the most visible aspects of the overall project: Two giant, translucent canopies outside the domestic terminal.