Find the terminal before anything else
There is no single domestic terminal at NAIA. Airline assignments are published by the airport authority in a current list sourced from the operator, and some carriers appear against more than one terminal depending on the service they run.
This is the detail that ruins otherwise well-planned trips. A traveller who assumes their domestic carrier is in the same building as their international arrival, and finds it is not, loses an hour they did not budget.
Read the terminal on your booking. If the ticket says only NAIA, ask the airline directly.
The transfer between terminals
The airport operates a free inter-terminal shuttle for passengers with connecting flights, running 24 hours, boarded by presenting your onward plane ticket. Published boarding points are the Terminal 1 arrival curbside, Bay 19 at Terminal 2, and the Terminal 3 arrival level.
It is a genuinely useful service, but it is a road journey with a queue at each end, and official pages have described its frequency differently, so it is not something to build a tight connection around.
One ticket or two
This distinction decides how much risk you are carrying.
On a single ticket with bags checked through, the airline owns the connection. If the first flight is delayed and you miss the second, rebooking is generally the airline's responsibility, and your job is to be in the right place.
On separate tickets, everything is yours. You clear immigration and customs on arrival, collect your checked bags, move them to the next terminal, and check in from scratch. A missed onward flight is your loss.
For a self-transfer at Manila specifically, the sensible minimum is generous. If your gap is under three hours on separate tickets, treat it as tight, and if it is under two, consider an overnight instead.
Baggage rules bite harder on domestic carriers
Domestic airlines in the region often price hand and checked baggage tightly, and the allowance on a domestic ticket bought separately has nothing to do with the generous allowance on your long-haul ticket.
Check the domestic allowance when you book, not at the airport, and pre-purchase any additional baggage online, which is nearly always cheaper than adding it at a counter. Weigh your bag before you leave your accommodation if you have been shopping.
The departure charge
A passenger service charge applies to departing passengers under an administrative order approved by government, with separate rates for international and domestic departures and a defined list of exempted passengers such as infants and crew.
For most travellers this is collected as part of the airline ticket, but it is worth confirming with your carrier, particularly on a separately booked domestic segment, so that you are not surprised at a counter.
Weather is the real variable
Domestic and island flights are the first services affected when a tropical cyclone approaches. The national weather agency records an average of 20 tropical cyclones in the region annually, with about eight or nine crossing the country, and a season peaking from July through October when nearly 70 percent of typhoons develop.
Practical planning during those months looks like this: avoid scheduling a domestic hop on the same day as an international departure, keep a spare day in the itinerary before any long-haul flight home, and check your airline directly rather than a third-party app when weather is developing.
A workable sequence
Confirm the terminal for each flight. Establish whether your bags are through-checked. If you are self-transferring, allow for immigration, reclaim, the shuttle, and a full check-in. Buy domestic baggage allowance in advance. Keep a buffer day before any international departure during the rainy season. Then the connection is a formality rather than a gamble.