Shares in the new American Airlines Group begin trading today as US Airways and AMR Corporation finalised their merger to create the world’s largest airline.

Labour groups from the old American will receive a 13.5% equity stake in the new carrier, valued at $1.04 billion.

The merger survived a challenge from the US government and criticism from consumer groups, who fear it will lead to higher prices.

The deal is the latest in a series of mergers that will leave four airlines controlling more than 80% of the US air-travel market and with more power than ever to limit seats and boost profits.

The combined carrier’s new chief executive Doug Parker, who held the same role at US Airways, told ABC News the biggest challenge was melding two complex organisations into one over time.

He said: “It’s not easy, but we have people that have done it before – both airlines have been through a merger in the semi-recent past. We have consultants on board who’ve done this with other carriers, so we’ll learn from what we’ve seen at others as well as what we’ve seen ourselves.”

The new American has a global network with almost 6,700 daily flights to more than 330 destinations in more than 50 countries. It has over 100,000 employees worldwide.

The airlines’ separate websites, and, as well as the two airlines’ reservations systems and loyalty programs, will continue to operate separately until further in the integration process.

US Airways will leave the Star Alliance on March 30, 2014 and enter the Oneworld airline grouping the next day.

With an expanded global network and a strong financial foundation, American will deliver significant benefits to consumers, communities, employees and stakeholders, a spokesman said.