Embraer is known for its regional jets that seat fewer than 130 passengers.
Production values of regional aircraft topped $7.1 billion this year and Embraer accounted for more than 45 percent of that, according to aerospace analysis firm Teal Group. Embraer's share is on track to top 56 percent by 2020, Teal Group projected.
"It's a hole in [Boeing's] product portfolio," said Jeff Windau, an industrials analyst at Edward Jones. "They've been focused on larger jets and one of their large competitors, Airbus, is expanding in that direction."
European aerospace giant Airbus is Boeing's archrival. The two companies compete on almost every type of aircraft, from single-aisle jets to widebody aircraft that can fit close to 400 passengers.
Airbus manufacturers the world's biggest passenger plane, the Airbus A380, a four-engine monster that can fit up to 800 people. That's a lot of arm rests to protect.
But the Toulouse-based Airbus is indeed delving into the small-jet market. In October, it swooped in to grab a majority stake in the struggling C Series program of Canada's Bombardier.
Delta agreed to buy at least 75 of the sleek, some 100-seat Bombardier jets last year. Boeing complained Bombardier dumped the planes below cost and used government subsidies. So far the Trump administration has agreed, slapping duties of nearly 300 percent on the jets. Delta hasn't taken delivery of the planes, but such tariffs would render them unaffordable.
Boeing argued before the U.S. International Trade Commission this week that Bombardier's sales practices hurt demand for its best-selling 737s. A final ruling is due by February.
Delta's CEO Ed Bastian has expressed confusion over Boeing's complaint because the U.S. company doesn't offer a small, competitor aircraft to the Bombardier C Series jets. Richard Aboulafia, vice president at Teal Group, said now that the Embraer talks have been brought to light, the suit makes sense.
"The trade complaint would suddenly be rational," he said, because Boeing would be sensitive about small-jet sales in the U.S.