Aerospace components manufacturer TransDigm Group Inc. announced on Wednesday it reached an agreement to buy Esterline Technologies Corp. in a deal worth $4 billion. The boards of both companies have approved the transaction in which Transdigm will pay $122.50 per Esterline share.

"The acquisition of Esterline expands TransDigm's platform of proprietary and sole source content for the aerospace and defense industries, including significant aftermarket exposure. Headquartered in Bellevue, Washington, Esterline is an industry leader in specialized manufacturing for these sectors with anticipated fiscal year 2018 revenue of approximately $2.0 billion," TransDigm said in a statement. The agreement is yet to be approved by Esterline's stockholders and is still subject to regulatory approval. The two companies expect the acquisition to be completed in the second half of 2019.

Esterline's shares soared over 30% in pre-market trading on the announcement.