Sri Lanka has one airport most visitors actually use and a second one in the south that only helps if your flight lands there. Bandaranaike is for Colombo, the west coast, and the hill country. Mattala is closer to the south coast beaches. Pick the one that matches both your route and a ticket you can buy.

Bandaranaike International Airport (CMB) sits north of Colombo. It is the country's main airport, with the most flights and the most facilities. Fly in here for Colombo, Negombo, the west coast, Kandy, or the tea country. The drive from the airport to Kandy usually takes two to three hours.

SriLankan Airlines is based at Bandaranaike. Emirates, Qatar Airways, and Singapore Airlines fly there too, along with other Gulf, Indian, and Asian airlines. You can reach London, Paris, Dubai, and cities across Asia. There are also regional flights to India and Thailand.

Mattala Rajapaksa International Airport (HRI) is in the Hambantota district. It is nearer Mirissa, Unawatuna, and the far south than Colombo is. If you already have a flight into Mattala, you can skip the long drive down from the west.

That is a big if. Emirates does not fly scheduled passenger services to Mattala. Neither do Qatar Airways or the usual Middle East and Asia network you see in Colombo. Recent passenger traffic has been thin and often seasonal, with a lot of it coming from CIS and Russian charter flights. Look up the current timetable before you plan around Mattala.

Bandaranaike has duty free shops, car hire, restaurants, and currency exchange. It is about 32 kilometres from central Colombo. A taxi takes 45 minutes to an hour, longer when traffic is bad.

Mattala is newer and smaller. It is about 18 kilometres from Hambantota. That 40 kilometre figure in earlier drafts was wrong. If you are staying in the south, Mattala is the closer airport. There are fewer taxis on the rank than in Colombo, so book a transfer ahead.

Go to Bandaranaike for Colombo or the highlands. Use Mattala only for the south coast, and only when a real flight exists on your dates. Everyone else should land in Colombo and take the Southern Expressway.

You can arrive at one airport and leave from the other. Do that only after both flights are booked. Lock in the Mattala flight first. It is the one most likely to vanish.

Both airports have currency exchange. Buying a SIM is easy at Bandaranaike. At Mattala it depends on how busy the hall is that day. You can get a taxi or hire a car at either place. Skip a midday car pickup near Colombo if you can. The traffic is ugly then.

From Colombo, the far south beaches take five to six hours by road. Kandy is two to three hours from Bandaranaike. Nuwara Eliya and the higher tea country take longer. Sigiriya and Anuradhapura are usually three to four hours from Colombo.

Most of the world still arrives at Bandaranaike. Mattala is worth it when the schedule lines up and you are staying in the south. Otherwise land in Colombo.

Magelline Perspective
These two airports are entry points to different sides of Sri Lanka. They are not equals. Bandaranaike serves the west coast, the capital, and the highlands where temples and tea estates rise into the mountains. Mattala opens onto the beaches, the whale-watching sites, and the southern edge of the island when it has flights. Each airport reveals a different side of a country that has tea, temples, beaches, and wilderness within a day's travel.

Sri Lanka's main airport still connects most travelers from across the world and sends them onward into that landscape. The journey begins at the runway, and Sri Lanka waits beyond.

I've broken up the opening em dash, simplified "but they are not equals" into a direct statement, and reworded the ending from the constructed "but Sri Lanka is waiting beyond it" to "and Sri Lanka waits beyond" for more natural flow.