Ninoy Aquino International Airport (NAIA) has four (4) terminals:

• Terminal 1 – is the international terminal for ALL foreign airlines except All Nippon Airways (ANA), which uses Terminal 3. It is located along the Ninoy Aquino Avenue from the NAIA Road.
  
• Terminal 2 – also called the Centennial Terminal because it opened in the year the Philippines celebrated 100 years of proclamation of independence from Spain (1998). It is used exclusively by Philippine Airlines (PAL) for both international and domestic flights. International flights use the north wing while domestic ones use the south wing. Recently, PAL transferred several domestic flights to Terminal 3, retaining only major domestic destinations at Terminal 2 (e.g., Cebu, Davao, Iloilo, Bacolod, etc.). For a complete list on which domestic flights are on T2 or T3, one can consult the PAL website. Terminal 2 is located at the end of NAIA Road.
• Terminal 3 – the newest of the three main terminals, it is located beside Villamor Air Base (actually part of it was carved out of the base) and across from the Resorts World Manila complex. It is used mainly by Cebu Pacific (Ceb Pac), currently the country’s largest airline, for both international and domestic flights. Other airlines using Terminal 3 are ANA and Airphil Express, which is a budget subsidiary of PAL. The terminal is located along Andrews Avenue at the end of Sales Road (from Fort Bonifacio).
• Domestic Terminal – now also called Terminal 4, it is the old terminal along the Domestic Road that used to be called the Manila Domestic Terminal where PAL, Cebu Pacific and other airlines used to operate domestic flights. At present, it is used by Zest Air and Seair.

More detailed information on these terminals may be found at the website of the Manila International Airport Authority (MIAA).

It is quite easy to transfer between domestic and international flights if you happen to fly Ceb Pac since all flights operate out of Terminal 3 and the airline provides assistance through its transfer desk. The same used to be the case for PAL when all flights were out of Terminal 2. But then after PAL transferred flights to Terminal 3, many passengers would now have to travel between Terminals 2 and 3. The most inconvenient cases are for travelers transferring to or from international flights at Terminal 1. Terminal 2 is quite near and can easily be reached via shuttle bus. The more challenging transfer is between Terminals 1 or 2 and Terminal 3. Shuttle buses would have to go through the NAIA Road, the Domestic Road the Airport Road

There are no internal connections between the 4 terminals operating within the NAIA complex such as AGTs, monorails. There are shuttle buses that travel between these terminals but they use the public roads rather than an internal road exclusive for the airport. As such, these shuttles are subject to traffic congestion and possible delays. The MIAA website states that using the shuttle buses are free but I saw a sign at Terminal 3 showing that there is a flat rate of PhP 20. While the fare would probably cover fuel, maintenance and other costs, it can also be argued that this service should be free at least for passengers and covered by airport authorities as part of the services they provide to travelers. Perhaps passengers can present their tickets before boarding the bus. Others may be required to pay the PhP 20 fare.

Bus station/stop at the NAIA Terminal 3 – the station is located at ground level (arrivals) beneath one of the overpasses (departure level) and across from the airport taxi stand (shown in the photo). Shuttle buses are scheduled to depart every 15 minutes according to the sign.

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