Shares of Archer Aviation soared Monday after the company announced it was taking over some of Boeing's subsidiaries as it adds to its flying-taxi and autonomous flight capabilities.

Archer Aviation stock rose 29% to $6.63 on Monday while Boeing stock declined 0.7% to $232.74. Archer shares entered the trading session down 26% this year.

The sharp share price increase Monday was in response to the announcement that Archer has agreed to acquire Boeing subsidiaries Wisk Aero, SkyGrid, and Insitu. Wisk Aero develops autonomous air taxis while Insitu makes drones. SkyGrid is an air-traffic software provider.

Archer estimated that the three companies will add a profitable defense business generating more than $200 million in annual revenue.

Boeing will receive an approximately 20% stake in Archer under the acquisition agreements, according to regulatory filings.

The acquisitions and architecture of the deal makes Boeing a strategic partner with and establishes ongoing Archer and Boeing "collaboration and technology sharing arrangement." The companies expect the deal to close by the end of 2026.

Archer Aviation is an electric vertical takeoff and landing, or eVTOL, aircraft maker. The company remains on track for flights in 2026.

The eVTOLs are quieter and easier to operate than conventional helicopters, opening up urban air taxi opportunities. Archer and its peers are on the cusp of commercialization.

Joby Aviation and Beta Technologies advanced 2% and 4.3%, respectively, on Monday.