Only a few hours after going on sale, Southwest airlines confirmed that their introductory $49 fares for flights to Hawaii are officially sold out.

The airline’s website shows that the lowest fares for flights from Oakland to Honolulu, which were available on Tuesdays and Wednesdays into June, are all gone.

By Monday afternoon, Southwest's website showed the majority of their flights to Hawaii for March, April, and May were completely sold out. While June still had availability, the cheapest tickets were listed now at $209.

Southwest said on Twitter that thousands of flights have been booked to Hawaii, but that more deals are still available.

The Dallas-based airline announced in 2018 that it planned on adding flights to Hawaii from San Diego, Sacramento, San Jose and Oakland.

Southwest will also launch inter-island service in late April. Flights will be available between Honolulu and Kahului beginning April 28, and between Honolulu and Keahole on Hawaii island beginning May 12.

On Twitter, the airline told one customer they're expecting on March 14 to have the remainder of their Hawaii schedule for sale through Nov. 2. 

The airline received approval from the Federal Aviation Administration to make long flights over water late last month in a process called ETOPS, or "extended range twin-engine operational performance standards" certification.

The airline had planned to launch flights to Hawaii in late 2018, but the partial government shutdown delayed the FAA approval. It's first test flight to Hawaii was on February 19.