Gov. Dannel P. Malloy signed a bill Friday that authorizes up to $400 million in tax breaks to United Technologies Corp. in return for the company’s investment of $500 million in four projects.

The deal negotiated by Malloy had broad bipartisan support in the General Assembly. UTC is the state’s largest private employer, and its two major aerospace subsidiaries, Pratt & Whitney and Sikorsky, also support an extensive subcontractor network in Connecticut.

“With the signing of this legislation, we are moving our state toward a new era of innovation, investment and economic growth, while solidifying our position as a world leader in aerospace manufacturing,” Malloy said in a statement. “Most importantly, this agreement has a direct impact on employment at the thousands of aerospace supply chain companies throughout the state, ensuring they are keeping and creating good-paying jobs with good benefits for men and women in nearly every city and town in Connecticut.”

The deal requires UTC  build a world headquarters and engineering facility on Pratt’s campus in East Hartford, expand the United Technologies Research Center, also in East Hartford, build a training center and engineering lab in Windsor Locks and upgrade facilities at Sikorsky, which is based in Stratford.