Holy shit shit shit THERE WAS A METHOD TO THE MADNESS. After 5 years away, AC852 has returned.
@airlineroute Air Canada increases Calgary - London Heathrow service from 7 to 9 weekly from 02MAY15, 11 weekly from 01JUN15 for summer season
AC850 YYC 1750 0935+1 LHR 333
AC852 YYC 1955 1150+1 LHR 763
AC851 LHR 1105 1351 YYC 333
AC853 LHR 1615 1835 YYC 763


Versus last summer on YYC-LHR:
77W x 7: 2443
(333 x 7) + (763 x 4): 2695
Seat gain of 252, so in terms of weekly seats it's the equivalent of daily 77W + a single 333.