The project would extend the standard-gauge line 45km beyond the airport to Seremban and a further 50km to Malacca to give these cities a direct rail link to KLIA and the Klang Valley. The projected cost of the extension is around Ringgits 8bn ($US 2.49bn) including rolling stock.

On May 2 the line was extended 2.1km to serve KLIA Terminal 2, offering a 33-minute journey time between the terminal and KL Sentral station.

The ERL was implemented as a 30-year finance-build-operate-maintain concession and opened in 2002. Two types of service operate on the route. KLIA Ekspress trains run non-stop between KL Sentral and KLIA Terminal 1 at 15-minute intervals during peak hours and 20-minute intervals at off-peak times with a journey time of 28 minutes. KLIA Transit services operate every 20 minutes at peak times and every 30 minutes off-peak, calling at the intermediate stations Bandar Tasik Selatan, Putrajaya & Cyberjaya and Salak Tinggi with a journey time of 35 minutes.