FedEx Corp. (FDX) Chief Executive Frederick W. Smith warned Wednesday of an "all-out air trade war" if the U.S. Congress moves to block efforts to further deregulate air travel between the U.S. and Europe.

Smith criticized a push in Congress to roll back provisions of the trans-Atlantic "open skies" treaty that went into effect last year. Under the treaty, European carriers can operate flights to the U.S. from any city in the European Union, and vice versa.

U.S. lawmakers should resist the "protectionist" urge to block additions to the treaty, Smith said in a speech at an aviation summit hosted by the U.S. Chamber of Commerce.

"Protectionism is tempting to political leaders when a market is shrinking and an industry is hurting," Smith said, adding that the U.S. "must simply turn back that tide."

He singled out an initiative in Congress, led by House Transportation and Infrastructure Committee Chairman James Oberstar, D-Minn., to tighten restrictions on foreign ownership of U.S. airlines.

The E.U. has made easing those restrictions a priority in the next phase of "open skies" talks, scheduled to begin later this year.

"We'll be in an all-out air trade war" if U.S. lawmakers push to roll back the trans-Atlantic treaty, Smith said.

-By Josh Mitchell, Dow Jones Newswires; 202-862-6637; joshua.mitchell@dowjones.com