Plane parts made in the U.K. are set to be exempted from U.S. import tariffs as part of the evolving trade agreement with Donald Trump’s administration, reports The Guardian.

U.S. commerce secretary Howard Lutnick has said that engines from Rolls-Royce and similar plane parts would be able to enter the U.S. market without tariffs, as part of a trade deal with the U.K. announced May 8.

However, The Guardian says, there were no references to the exemption in a five-page document released in the aftermath of the deal’s announcement on May 8 setting out the terms of the “economic prosperity deal,” and final details are still to be determined.

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The U.K. businesses secretary, Jonathan Reynolds, told the Sunday Times that the wider aerospace industry would have “a specific guarantee of zero tariffs” in the agreement.

The deal would be a relief to a £40 billion ($53 billion) sector, which supports 450,000 jobs in the U.K.

The deal would also be important to the U.S., as Boeing imports Rolls-Royce engines for its commercial airliners, and repair and maintenance facilities based in the U.S. also require a regular flow of parts.