Commuter Line. As of 2021, the three systems and its four operational lines combined has 82 stations, covering a total of . The network makes up the majority of active railways in the country and bear the brunt of providing the metropolis with rail as a faster alternative mode of transport other than buses and jeepneys. However, these systems are currently insufficient for the rapidly expanding metropolis; to address this, new lines and line extensions are under construction, which will extend the system far out into neighboring regions. Several new railway projects are being undertaken by the national government and the private sector. These include the North–South Commuter Railway, the Metro Manila Subway, and MRT Line 7, all of which are under construction. Line extensions such as the LRT Line 1 South extension and the LRT Line 2 West extension are in the pipeline. Other line extensions and railway lines are in the planning stage. Air Ninoy Aquino International Airport (NAIA) is the only airport and the premier gateway in Metro Manila. It is the busiest airport in the Philippines. NAIA has four terminals: Terminal 1, Terminal 2 (which is exclusively used by Philippine Airlines), Terminal 3 (the newest and largest airport terminal in NAIA) and Terminal 4 (also known as the Manila Domestic Passenger Terminal). The other airport that serves Metro Manila is Clark International Airport in Angeles City which is located away. Buses Bus franchises in the region are regulated by the Land Transportation Franchising and Regulatory Board. The Premium Point-to-Point Bus Service is the express bus system that runs from its dispatch terminal in Fairview up to the central business districts along EDSA. It aims to cut travel time substantially and provide a faster, safer and more convenient bus service to commuters, who are usually caught at the heavy traffic across the metropolis. A second express bus link from SM North EDSA, Trinoma and SM Megamall to Makati opened in December 2015, and by January 2016 was the line on which, for the first time in nearly three decades, a double-decker bus traveled on EDSA, to the delight of motorists, followed by a third link, this time from Robinsons Galleria to the Ayala Center complex in February 2016 and a fourth in March linking the Ayala Center to the Alabang Town Center in Muntinlupa via the Metro Manila Skyway (and later to Ayala Malls South Park). As