Airbus members celebrate the landing of an Airbus A220-300 aircraft during its presentation in Colomiers near Toulouse, France, July 10, 2018.

Bombardier's shares fell 37% on Thursday after the company warned its 2019 profits would be lower because of problematic rail contracts and said it might have to write down the value of a plane partnership with Airbus .

Bombardier, which sold control of the A220 narrowbody jet to Airbus in 2018 as part of a long-running drive to put it on a solid financial footing, said the venture needed more investment and might be subject to a writedown during fourth quarter results next month.

The Canadian plane and trainmaker is shedding underperforming commercial plane programs to focus on its more profitable business jet and rail units.

But Bombardier's rail division, its largest unit by revenues, is wrestling with three rail projects in Europe, resulting in a $350 million charge. "Although Bombardier's transportation segment has been volatile, cost problems out of Europe look worse than the market has been anticipating," Citi analyst Stephen Trent said in a note to clients.

Bombardier now expects 2019 adjusted earnings before interest and taxes (EBIT) to be about $400 million, compared with a previously forecast range of between $700 million and $800 million.

Free cash flow, a metric closely watched by investors, is expected to be negative $1.2 billion in 2019, compared with the previously forecast negative $500 million.

Shares fell as much as 38.6% in morning trading to C$1.10 ($0.8436), the company's biggest decline on record. The yield on Bombardier's U.S. dollar bond due March 15, 2025 surged more than 150 basis points to 8.4%.

Bombardier has $9.7 billion in outstanding bonds, according to Refinitiv data.

Bombardier also said it is "reassessing" its minority stake in the A220 jet program, which will require additional cash to ramp up production.

Under the terms of the 2018 deal, Bombardier could oblige Airbus to acquire its 33.58% stake in the program in 2026 at market value or Airbus could oblige Bombardier to sell the stake. But Bombardier has previously said the parties are free to transact earlier if they both agree.

Airbus, which has a 50.6% stake in the A220 program, said it remained committed to funding the jetliner on its way to profitability.

While some analysts see it as a negative for Airbus, others say the pain of putting up more money would be relatively small for the European planemaker compared with the long-term benefits of acquiring the A220.

The deal shores up Airbus's position at the lower end of the narrowbody market where rival Boeing plans to expand by acquiring Brazilian planemaker Embraers commercial arm.

"Airbus have effectively acquired somewhere between $5 and $8 billion of R&D for a song; they have gained a market position that they would have never invested in; and they will have the ability in future to respond to changes in the market at a lower cost, said Sash Tusa, aerospace analyst at UK-based Agency Partners.

Bombardier said the program was "winning" with airlines, but would take longer to break even.

"This may significantly impact the joint venture value," the company said, adding that it would disclose any writedown when it reports final fourth quarter and 2019 financial results on Feb. 13.

Questions over the company's stake in the A220 come as Bombardier is facing pressure to pay down its debt and bolster its rail unit, said a source familiar with the company's thinking.

"It is a cash deployment question," the source said.

A spokesman for the economy minister in the Canadian province of Quebec, which holds a 16.36% stake in the A220 program, declined to comment.

Bombardier also said delivery of four of its Global 7500 jets, which list for $73 million each, had now slipped into the first quarter of 2020.