Delta Air Lines will leave Airlines for America (A4A), the group that lobbies on behalf of the US airline industry, in 2016.

The move by the world’s and US’s second largest airline in terms of revenue, which will take effect April 26, 2016, is a blow to A4A’s mission of presenting a united front of US carriers as it lobbies Congress and the White House on major industry issues.

A4A said in a statement that Delta’s departure “was not unexpected as the carrier has not been aligned with other A4A members on a few key industry positions, including the need to modernize and improve the nation’s air traffic control system.”

A4A has pushed for “a commercialized, non-profit type governance structure” for US air traffic control.

A4A president and CEO Nicholas Calio said in a statement that Delta’s departure “will not distract A4A and its members from the continuing work of fighting higher taxes and unnecessary regulations while pushing for updated infrastructure along with the vast array of technical and regulatory issues that A4A’s councils and committees regularly address.”

In an emailed statement, Delta said, “The $5 million that Delta pays in annual dues to A4A can be better used to invest in employees and products to further enhance the Delta experience, and to support what we believe is a more efficient way of communicating in Washington on issues that are important to Delta customers and employees.”

American Airlines chairman and CEO Doug Parker, who is serving as A4A’s current chairman, said US airlines “have been and will continue to be more effective as an industry advocating for our customers and employees with a unified voice in Washington, and we are committed to working with A4A to achieve reform at the highest levels, including air traffic control.”

The split comes amid the debate over FAA reauthorization; the agency’s authority has been temporarily extended to March 31, 2016, and Congress is expected to take up the issue early next year. “With FAA reauthorization, we have an opportunity to address [flight] delays that cost $30 billion annually and implement transformational change to the air traffic control system that would mean greater efficiency and a better travel experience,” Calio said.

Although not referenced by A4A, Delta or American’s Parker, there has also been a split among A4A member airlines on the issue of Open Skies and state subsidies for airlines. Delta and CEO Richard Anderson led the campaign to get the alleged subsidies of Emirates Airline, Etihad Airways and Qatar Airways exposed and to get the US government to investigate whether those Gulf-based airlines are abiding by the fair competition rules of the Open Skies agreements between the US, the UAE and Qatar.

Although American and United Airlines joined Delta in the campaign, other US carriers are against it. A4A, like IATA, has taken no stance on the issue.