Alaska Air Group has completed its acquisition of Virgin America, a deal that was signed in April and approved by Virgin shareholders in July.

The merger makes Alaska the fifth largest carrier in the US and the largest airline outside of the “Big Four” carriers – Delta, American, United and Southwest – which control 84 per cent of domestic American air travel.

The airlines have a combined fleet of 286 aircraft with an average age of eight years – younger than any of the fleets in the Big Four.

Alaska Air Group now serves more nonstop destinations from the West Coast than any other airline, and operates the largest number of West Coast hubs.

The merger also increases Alaska’s access to East Coast destinations such as Washington DC and New York City.

The carrier has announced that it will add daily services from its newly acquired hub in San Francisco to Orlando, Minneapolis and southern California from summer 2017. These will be available to purchase online from December 21.

The two airlines will begin to merge loyalty programmes from December 19, when Alaska Airlines Mileage Plan members will be eligible to receive rewards on Virgin America flights and vice versa. Virgin America Elevate members will be invited to activate Alaska loyalty programme accounts from January 9 2017.

The two airlines hope to secure certification to operate as a single carrier from the US Federal Aviation Administration next year, but Alaska has not yet made a final decision on how it intends to use the Virgin America brand.

“We appreciate that there is great interest in the future of the Virgin America brand among customers and employees alike,” said Alaska CEO Brad Tilden.

“This is a big decision and one that deserves months of thoughtful and thorough analysis. We plan to make a decision about the Virgin America brand early next year.”

Passengers can purchase Virgin America tickets on Alaska Air’s website from December 19.