SYDNEY — The first international flight took off Monday from a new, multi-billion-dollar airport in the fast-growing western suburbs of Sydney.

After more than four decades of planning, Western Sydney International Airport offers the first alternative to the city’s main airport, which has been operating for more than a century.

An Air New Zealand plane from Auckland landed and soon afterwards flew out of the airport in the morning, launching a three-flights-a-week service to Sydney’s largely working-class western suburbs.

“It’s not every day you get to be part of opening a brand-new international airport,” said Air New Zealand chief operations officer Kate Boyer.

“Western Sydney is home to more than 2.5 million people and it’s a further gateway for Australian visitors to discover everything our country has to offer.”

The new single-runway airport, Australia’s first new major aviation hub in more than five decades, began domestic flights on Sunday, and freight operations in July.

Sydney’s main airport, Kingsford Smith, is Australia’s busiest, its three runways handling more than 42 million passengers last year.

Lying in Botany Bay just nine kilometres (six miles) from the city centre, planes using the airport roar over many city homes, and a curfew bars passenger aircraft from operating during the night.