German airline Lufthansa is buying a 19% stake in US budget carrier JetBlue Airways for $300m (£147m).
Lufthansa is buying into the domestic US market
In a joint statement, the two companies said the deal represented the first significant investment by a European airline in a US carrier.
The move follows after Lufthansa said in October that it was planning a major investment drive.
New York-based JetBlue operates between 53 American cities, with up to 550 flights each day.
Back in October, JetBlue reported its first third quarter profit in two years, as fuller flights offset higher costs for fuel and other items.