by Andy W » 15 Aug 2011, 14:11
Hi Sue. I did the research on Thomas Cook's flight-only website
Because the flights are used for 7, 10,11 and 14 day packages, as well as people booking flight only, as well as seasonal fluctuations, there's often a load imbalance between the outward and return legs of a flight. This means as you've found, it can be cheaper to book outward on one half of a pair of flights and return on another, but 7 or 14 day packages are normally sold on the basis of using both flights in the pair. Thomas Cook use even numbers for the outward flight and odd numbers for the return.