United Airlines and Air Canada, both Star Alliance members, have launched a joint promotion to offer bonus miles on flight between North America and London.
If you tend to fly economy to North America, this is a pretty decent deal as most (all?) fare classes are included.
The promotion is relatively simple. You will earn:
7,500 bonus miles for flying two segments (ie a round trip)
10,000 bonus for flying a further two segments
15,000 bonus miles for flying a further two segments
…. making a total of 35,000 bonus MileagePlus or Aeroplan miles for three round trip flights or six one-way flights.
You need to register with EITHER United or Air Canada. However, flights on BOTH airlines will count as long as they are credited to the scheme you registered with.
If you look at the Air Canada Aeroplan registration page there is no small print. It gives the impression that you only earn the bonus on flights which start in North America. The terms and conditions confirm that flights in either direction are OK.
Similarly, on the United registration page, the rules make it clear that it works in either direction.
If you fly a lot to North America, you may even be able to earn this bonus twice. Credit your first three return flights to one programme and then credit your next three return flights to the other.
All travel must be completed by December 12th. Note that you will only earn the bonus if your booking was made after September 15th.