Air India is upgrading aircraft deployed on the Heathrow-Delhi route and increasing capacity.
An extra 336 seats a week will be available from September 1 when an Airbus A350-900 is introduced.
The aircraft will replace Boeing 777-300ER and Boeing 787-8 Dreamliners on 14 of 17 weekly flights.
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The new aircraft will enable Air India to introduce premium economy for the first time on the route with A350-900, offering 24 wide seats in a 2-4-2 configuration in a dedicated cabin.
The carrier will have upgraded 90% of all its flights from Heathrow with the deployment of the A350-900.
Air India started using Boeing 777-300ERs with elevated cabin interiors on all Heathrow-Mumbai flights in April to provide upgraded cabin interiors and in-flight entertainment systems, while bringing first class back to the route.
Airline chief executive and managing director Campbell Wilson said: “The deployment of our flagship A350s and the B777s with upgraded cabin interiors to London Heathrow marks a significant milestone for Air India.
“It demonstrates our commitment to elevating the travel experience of our guests to truly world-class standards and to going beyond just meeting customer expectations as we continue to renew our fleet.
“With our industry-leading cabin products on the A350 including a new premium economy experience and a host of new on board enhancements rolling out, we are confident that these daily flights between India and London Heathrow will soon be the preferred choice for travellers.”