Brazilian aircraft manufacturer Embraer said Saturday that Boeing "wrongfully terminated" a deal for a $4.2 billion tie-up, an ugly turn that comes as both companies face a dismal market for commercial jets amid the coronavirus pandemic.

Boeing earlier on Saturday said it ended talks that would have given the Chicago-based aerospace giant an 80% stake in Embraer's commercial jet unit. Boeing said Embraer did not satisfy conditions under the agreement, which expired late Friday, but Boeing declined to go into specifics.

"It is deeply disappointing. But we have reached a point where continued negotiation within the framework of the [merger transaction agreement] is not going to resolve the outstanding issues," said Marc Allen, president of the Embraer Partnership and Group Operations, in a Boeing news release earlier Saturday.

But Embraer said the deal was "wrongfully terminated" and vowed to "pursue all remedies against Boeing for the damages incurred."

Boeing is required to pay $100 million if antitrust approvals for the deal aren't secured, according to a company filing, but a Boeing spokeswoman said the company doesn't believe that the termination fee applies in this case.

Boeing "manufactured false claims as a pretext to seek to avoid its commitments to close the transaction and pay Embraer the US$4.2 billion purchase price," Embraer said. "We believe Boeing has engaged in a systematic pattern of delay and repeated violations of the MTA, because of its unwillingness to complete the transaction in light of its own financial condition and 737 MAX and other business and reputational problems."

The deal, which would have given Boeing control over Embraer's commercial jet arm, was meant to help Boeing grow even stronger in commercial aerospace to better compete with European rival Airbus. Airbus, for its part, has already taken a stake in what's now called the A220 passenger-plane program of Canada's Bombardier.

The collapse of the Boeing-Embraer deal comes as the aerospace industry is in crisis because of the coronavirus. Thousands of jets around the world are grounded as air travel demand has dried up in the pandemic and shelter-in-place orders that aim to stop it from spreading. The crisis has put airlines on shaky financial footing that's destroying demand for new jets and accelerating retirements of older planes

"When nobody is flying and jets are on the ground it's hard to hard ascribe winners and losers" in the collapse of the deal, said Richard Aboulafia, vice president of analysis at Teal Group.

Boeing announced the terms of the deal in July 2018, which would have given it control of Embraer's commercial aerospace arm, which makes passenger planes that are smaller than Boeing's jetliners. That could have opened up a new market for Boeing. It also could have gained access to Embraer's engineers to help it design and test a new mid-size passenger plane, Aboulafia said, a plan that has been upended by the 737 Max crisis and now the pandemic.

Embraer, without Boeing, will compete against Airbus, which has a lower cost structure, for some segments of the smaller passenger-jet market, Aboulafia added.

Much has changed for Boeing since the talks were first disclosed in late 2017. Two of its 737 Max planes, its best-seller, crashed, one in Indonesia in October 2018 and another in Ethiopia in 2019, killing all 346 people on the two flights.

Those jets have been grounded since March 2019 and cancellations are piling up, promising a painful year for Boeing.

Boeing is expected to provide more detail about the deal and further plans to cut costs when it reports first-quarter results before the market opens on Wednesday.