British Airways owner International Airlines Group and Qatar Airways are establishing a joint business to codeshare on flights between the UK and Doha.
The Gulf carrier is a 20% shareholder in IAG having increased its stake in August.
The BA-Qatar Airways partnership comes into force on October 30 to provide better links between the UK, Asia, Middle East and Africa.
Passengers will be offered a combined route network covering more than 70 destinations.
The new partnership will offer seven daily non-stop services in both directions between the airlines’ hubs in London and Doha.
The agreement will also strengthen the Oneworld alliance and enable it to compete more effectively on the routes by creating greater competition and increased options for consumers.
Qatar Airways chief executive, Akbar Al Baker, said: “This partnership brings together two world-class airlines to provide an enhanced operation for our passengers with increased daily flights between London and Doha, greater choice of flight schedules, wider range of fares and improved members benefits.
“Today’s announcement reinforces our already established relationship with IAG and we look forward to welcoming British Airways’ direct flights to our hub, Hamad international airport, where we can provide passengers with seamless access to our global network of more than 150 destinations.”
IAG chief executive, Willie Walsh, said: “This agreement will benefit customers by giving them access to more destinations through Qatar Airways’ extensive network.
“It will also allow us to provide easier journeys with better aligned schedules, more frequencies and improved flight transfers.
“This partnership follows the commercial agreement with IAG Cargo signed two years ago and enhances our relationship with Qatar Airways further.”