United Airlines Mileage Plus and Air Canada Aeroplan members who fly between London and North America can earn up to 35,000 bonus miles.
The promotion applies to non-stop return flights on either Star Alliance carrier between September 23 and December 12.
Members can earn 7,500 bonus miles for their first round-trip, 10,000 for their second, and 17,500 for their third, making a total of 35,000 bonus miles. They need to register for the offer prior to travel, using promotional code TB9M76.
Members can choose to earn miles in either Mileage Plus or Aeroplan, but not both. Only one registration is eligible per booking.
In June, United announced that its Mileage Plus members will from next year earn award miles based on ticket price rather than distance flown (see news, June 11).