The US International Trade Commission's ruling in favour of Bombardier did not hinge on some obscure legal technicality in the end.
Rather, the decision came down to a straightforward conclusion: that the smallest version of Boeing's 737 family does not directly compete with the CSeries.
Therefore, subsidies and price dumping aside, Boeing suffered no harm by Bombardier's 2016 sale of 75 CS100s to Delta Air Lines, according to the ITC's full investigative report released on 14 February.
"Delta did not consider any new 100- to 150-seat [aircraft] from Boeing because the 126-seat 737-700 and the 138-seat 737 Max 7 were unsuitable for the mission profile in question," says the report.
The nearly 200-page document explains why the ITC's four commissioners all voted "negative" to whether Bombardier's sale hurt Boeing on 26 January.
"Specific airlines engaged in purchasing campaigns may not consider CSeries aircraft to be substitutable with the 737-700 or 737 Max 7, particularly if they are seeking to acquire aircraft for mission profiles that require fewer seats," the report says.
The bottom line: "We determine that an industry in the United States is not threatened with material injury by reason of imports of 100- to 150-seat [aircraft] from Canada that are sold in the United States at less-than-fair value and that are subsidised by [Canada]."
Bombardier says the report sweeps away any doubt about the opinions of the ITC's four commissioners, freeing Bombardier to progress with CSeries deliveries from Canada to US customers, starting with Delta Air Lines.
"The ITC ruling clears the path for us to support Delta this year as we work to close our partnership with Airbus," says Bombardier. "The ITC correctly recognised that the 737 family of aircraft, with a deep backlog and record profits, is not under threat."
"We are moving full speed ahead with finalising our partnership with Airbus… We look forward to delivering the CSeries to the US market," Bombardier adds.
Delta previously told the ITC that it intended to only take CSeries from Bombardier's proposed assembly line Alabama, not from Montreal Mirabel.
"As the ITC notes, we have contractual commitments to begin taking deliveries later this year and the ITC decision clears the way for Delta to accept deliveries in Canada as well," Delta says in a statement. "Delta still intends to take as many deliveries as possible from the new Airbus/Bombardier facility in Mobile, Alabama, as soon as that facility is up and running."
No problem, says the ITC.
"Delta might indeed import at least some, if not all, of the CS100s due to be delivered pending any renegotiation of the terms of its contract with Bombardier," says the ITC's report. "We do not find, however, that Delta’s imports of CS100s from Canada will come at the domestic industry’s expense."
Bombardier says it intends to move forward with the Alabama site despite winning the dispute.
Boeing declines to comment, saying it is reviewing the report.
Though the Chicago-based airframer could still appeal, the release of the ITC's report largely concludes the trade dispute launched by Boeing in April 2017.
Boeing alleged in a petition to the US Department of Commerce that a heavily-subsidised Bombardier dumped CS100s to Delta at an artificially-low price of $19.6 million each, harming Boeing's sale of 737-700s and 737-7s, and violating US trade law.
The Delta sale, and an allegedly lowball CSeries offer to United Airlines, threatened the "viability" of the small 737 models, former Boeing vice-chairman Ray Conner told US trade officials last year.
Bombardier and Delta fought back, insisting that the smaller CSeries does not compete with any 737s. Delta said the only aircraft Boeing offered to meet Delta's needs were used Embraer 190s.
The petition kicked up concurrent investigations by the US Department of Commerce and the ITC.
Last year, the Commerce Department ruled in Boeing's favour, slapping CSeries imports with 292% import tariffs.
Seemingly facing a devastating loss in trade court, Bombardier partnered with Airbus in October 2017, unveiling plans to assemble the CSeries in Alabama in a move the company said would free the aircraft from import duties.
As part of the deal, Bombardier intends to hand 50.01% of the CSeries programme over to Airbus in exchange for marketing, sales and procurement support, with no money changing hands. The companies say the deal will close in the second half of 2018.
But the ITC held the final card.
To many observers' surprise, on 26 January the ITC ruled that Boeing actually suffered no harm by Bombardier's sale, a decision that swept away the 292% import duties.
'SMALL MAINLINE AIRCRAFT'
The just-released final report delves into that decision, discussing particulars of trade law, legal definitions, airline economics and aircraft performance.
The ITC actually upheld Boeing's argument that the CSeries and 737-700/Max 7 occupy the same market segment. It also agreed that airlines can, to a "moderate degree" substitute those 737s for CSeries.
But those points are moot because Delta did not want an aircraft as large as the 737, the report says.
Delta, in 2015, launched a campaign specifically aimed at purchasing a "small mainline aircraft" with 100-110 seats to replace regional aircraft, notes the ITC.
The airline considered purchasing four aircraft models, none of them currently made by Boeing: 109-seat CS100s, 96-seat E190s, 100-seat Embraer 195s and 110-seat Boeing 717s.
"Because Boeing did not lose this sale to Delta, Delta’s imports of CS100s will not displace domestically produced 100- to 150-seat [aircraft] from the US market," the report says.
The ITC notes that Spirit Airlines and JetBlue Airways likewise agreed that the CSeries does not compete directly with the 737s.
The commission drilled holes into other arguments made by Boeing, including its contention that the Delta deal will propel Bombardier to more US sales.
Indeed, other airlines like Spirit and JetBlue have expressed interest in CSeries.
"We find insufficient evidence to conclude that Bombardier is likely to secure additional sales… in the imminent future", the report says. Even if Bombardier does land more deals, Boeing will not suffer, it adds.
The ITC finds "mixed" evidence that CSeries competed with the 737-700 for United's business. Boeing said it won that sale only after CSeries pressure pushed prices down.
But the ITC says Boeing "lost no revenue" because United later converted its 737-700 order to larger 737 variants.
Boeing also claimed that Bombardier's Delta sale would depress future sale prices. The ITC questioned that claim, too, noting that other manufacturers likewise use discounted "launch pricing".
"Boeing offered substantial discounts on many orders for out-of-scope 787 [aircraft] during the years following the new model’s launch in 2004, but then secured substantially higher prices on subsequent orders," says the report.