None of the airfare search engines are reliable. They all claim to find the best fare. Try searching for a non-Saturday night stay trip, EWR-ORD. For example, from EWR to ORD on 4/23 and return on the 24th. Remember that I want the lowest fare. The correct answer is $429 on NW with a connection in DTW. This can only be found on the NW search engine.Virtually all the search engines quote $ 1,037. The moral of the story is to check all possible sites if you really want the lowest available airfare.