The coordinated settlement agreement that lifted a legal cloud over Airbus was the product of an extraordinary, multiyear collaboration among five top-tier law firms in three countries, working closely with Airbus and national authorities in a “virtual law firm” whose size and scope was unprecedented, according to lawyers involved.

Airbus will pay a total of 3.6 billion ($4 billion) to authorities in France, the U.K. and the United States to settle a four-year-long investigation into accusations that the aerospace giant, based in Toulouse, France, arranged bribes to sell its products between 2004 and 2016 in violation of International Traffic in Arms Regulations.