In a fresh filing with the U.S. International Trade Commission, Bombardier says it has made "substantial further progress" toward building a new aircraft assembly line in coastal Alabama.

The news is the latest twist in high-stakes maneuvering among some of the world's biggest aerospace companies. Bombardier is locked in a trade dispute with Boeing; Airbus and Bombardier have formed a joint venture and say they want to assemble jets in Mobile; and Boeing, which has scoffed at the Airbus-Bombardier plan, has explored a relationship with Brazil's Embraer that has some similar aspects.

Bombardier's latest information was filed in relation to its dispute with Boeing, whose representatives have argued that the proposed assembly line in Mobile likely will never come to pass. (If it does, it'll be a site where the Bombardier-Airbus venture CSALP will produce Bombardier's C Series jets.)

In its latest filing, a law firm representing Bombardier cautions that the trade commission "should keep in mind the legal restrictions limiting how much planning can be implemented pending receipt of all antitrust approvals." In other words, CSALP has to get governmental green lights before it can really step on the gas. It says pre-merger clearance is required from Germany, Austria and one or more other countries redacted from the publicly available version of the document.

While substantial portions of the document are not publicly available because they contain proprietary business information, Bombardier says that because it already has established a C Series Final Assembly Line (FAL) in Mirabel, Quebec, it is "well-positioned to efficiently replicate the Mirabel assembly line in Alabama." It references "new developments with respect to site planning and construction" which are omitted from the public document.

The document:

references certification from the FAA and its Canadian counterpart, the TCCA, suggesting that Bombardier has begun the process

says that Bombardier "has identified all of the equipment and tooling that will be required to establish and operate" the FAL

says that Bombardier "has prepared a human resources plan for staffing the U.S. FAL" and suggests it has set a timetable (which is omitted) for active recruitment

and says that "In sum, planning for the U.S. FAL is now at an advanced stage, with nearly every aspect of the U.S. FAL having been planned in detail."

Later this month, the International Trade Commission is expected to rule on Boeing's claim that Bombardier's C Series pricing is unfairly low due to Canadian government support. It could opt to uphold tariffs of nearly 300 percent on imported C Series jets.

Having a FAL on U.S. soil could help avoid such tariffs if they are imposed, but a clear end to the corporate dispute isn't necessarily in sight. Boeing has said that a tariff should still apply to components imported to a domestic FAL, while Bombardier has argued that a large portion of its components are originally produced in the U.S.