United Airlines on Wednesday announced a major international expansion at San Francisco International Airport.

The airline said it plans to add flights between San Francisco and Melbourne, Australia, New Delhi, Toronto and to boost service to Amsterdam and Seoul, South Korea.

United CEO Oscar Munoz, in a conference call with reporters, said it's the largest international expansion United has ever done in San Francisco.

"We really feel it secures United as the premier gateway to the Pacific,'' he said.

United had teased the new routes as a "historic package of new and expanded international routes'' prompting hours of online speculation about the new flights, including possible flights to Africa. (No flights to Africa were announced.)

"It's a capstone to 2018, which I think truly is a breakthrough year for United,'' Munoz said.

Details on the new flights:

San Francisco to Melbourne: Three weekly nonstop flights on a Boeing 787-9 Dreamliner beginning Oct. 29. The airline already offers service to Sydney from San Francisco and flights to Sydney and Melbourne from Los Angeles.

San Francisco to New Delhi: The seasonal service begins Dec. 5 on a Boeing 787-9 Dreamliner. United currently offers nonstop flights from Newark to New Delhi and Mumbai, India.

San Francisco to Toronto: United will offer two daily flights beginning March 31 on a Boeing 737-800. United already offers daily service between San Francisco and Calgary and Vancouver, Canada. It serves Toronto from most of its major hubs.

With the new flights, United will serve 29 international destinations from San Francisco. The airline said it has added 12 new international destinations at the airport since 2013.

The new routes are part of an aggressive international expansion by United this year.

In November, the airline announced plans to start service between its Denver hub and Frankfurt, Germany, in 2019 and said it wants to add a second daily flight between Newark and Shanghai in 2020.

In August, United announced new service to Prague and Naples, Italy, from Newark, and new flights between San Francisco and Amsterdam. The airline will be the only carrier offering nonstop service between the United States and Naples when the seasonal flights begin May 22.

Also in August, United said it plans to add nonstop flights between Washington Dulles and Tel Aviv, Israel, in 2019. It will be the airline's fourth flight to Israel. United has two daily flights from Newark to Tel Aviv and daily flights between San Francisco and Tel Aviv.

United also announced plans to increase service between San Francisco and Auckland, New Zealand, in 2019.

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