cheapest way to book long haul flights

[ooo000ooo]

I've been checking flight prices on Expedia regularly the last week. Checked yesterday and there were only 2 flights available to LAX with massive lay over times at different airports. Thought bks flights have sold out already.
Went into TripAdvisor put the same details in and found the same flights I'd been watching plus a load of others that would work and TripAdvisor linked back to Expedia!
How does that work?