Arconic has signed a new long-term contract with Boeing (NYSE: BA) to supply aluminium sheet and plate for all models produced by Boeing Commercial Airplanes.

The multiyear contract, which extends and adds to the companies’ 2014 contract, is the largest to date and captures growth in the build rate increases of the Boeing 737 program.

“This agreement demonstrates Arconic’s commitment to deliver quality and innovation to our customers,” said Tim Myers, President of Arconic Global Rolled Products and Transportation and Construction Solutions. “We’re proud of our more than 40 years of collaboration with Boeing, and we look forward to playing a role in their continued success.”

The new agreement builds on Arconic’s collaboration with Boeing for wing skins on all of its metallic structure airplanes and includes polished fuselage skins and wing ribs. In addition, Boeing awarded Arconic new business for the supply of structural plate used on a variety of other applications, including wing ribs for carbon fibre platforms such as the 787 and 777X.

The deal draws on material produced by Arconic’s Very Thick Plate Stretcher (VTPS), which began commercial production last year and is capable of stretching the thickest aluminium plate in the world, used to support composite wings. Combined with its new horizontal heat treat furnace, which is expected to begin qualifications in 2019, Arconic is able to offer expanded capabilities and capacity in thick plate products. One of the challenges composite wing makers face as the wings get larger is maintaining their structural strength and stiffness. Aluminium plate from Arconic’s stretcher enables aircraft manufacturers to address that issue. As a result, demand for thick aluminium plate is growing, particularly as larger composite wings, made with monolithic thick plate wing ribs, increases.

Under this agreement, the companies will also continue to collaborate on new, high-strength and corrosion-resistant alloys, including aluminium-lithium that could be used for complex structural applications.

Arconic’s aerospace business, which had revenues totalling more than $5 billion in 2017, holds leading market positions in aerospace sheet and plate produced by its Global Rolled Products (GRP) business and in aerospace forgings, extrusions, jet engine airfoils, structural castings and fastening systems produced by its Engineered Products and Solutions (EP&S) business.