Luthansa's subsidiaries Austrian Airlines and Swiss International Air Lines will become members of their parent company's Atlantic++ joint venture in July, after sister carrier BMI signed up earlier this month.
Austrian, Swiss and BMI are not joining as individual carriers, but will be under the Lufthansa Group umbrella, a spokesman for the German flag carrier says.
The aim of the revenue-sharing partnership is to better co-ordinate the airlines' flights on transatlantic routes between America, Europe, Africa, the Middle East and India. Aside from Lufthansa, the joint venture includes Star Alliance carriers Air Canada and United Continental.
While BMI became a member this month, Austrian and Swiss will join Atlantic++ on 1 July.
Brussels Airlines, also part-owned by Lufthansa, has not joined because Lufthansa holds only a 45% stake in the Belgian carrier.