I don't think they use searches. There was a very interesting piece on TV a few years ago about how revenue management looks at historic data and already booked seats to predict loads. If they see that a flight has a lighter load than is expected for n weeks out, they will release cheaper seats. If they flight has a higher load they will withdraw cheap seats. This also explains why sometimes at between 4 and 8 weeks out prices sometimes go down, before they go up again as the advance purchase thresholds kick in.