Search engines are not made to find the cheapest flights. Cheapest flight only deals to be found to see that any particular company has in place at their Hot Deals section or in places such as supply SkyAuction.
I know this is not the kind of start you'd expect from an article in which I was supposed to promote search engine, but I just want to be sincere with you. This is not the best solution.
Once this is explained, for people who really have the time and want to find a quick alternative to buying their flight in a way that probably is not the cheapest but can find a deal that is more or less well in a very few seconds, I must say that it there is a search engine that puts together the other search engines plus all existing crucial airlines.
Qixo his name, not knowing of the most known search engines, but basically he would gather all the quests you can do with Cheaptickets, OneTravel, Travelocity and Priceline in a single operation.
You will notice that instead of being given the results after waiting for 10 seconds or more, you will be given a countdown of 70 seconds. When this happens, the first results will show, and another countdown will begin at the same show more results. In general, the first result you'll find the first flight at the top of the page as the cheapest, but you can just let the machine do a complete search and how do you make sure that nothing is left behind.
You can also use it in the same way as any other travel machine in order to find accommodation, cruise, vacation packages, etc. You can also get affiliated to the system, and earn some commission from the people who travel books through your affiliate URL, which I do not would recommend either, because eventually people will find that search engines are very good looking but never do what they want to do.
Simply, choose this method if you are in a hurry, and use it if you're one of those who want to stick with the search engine to die. You will have the same result if you see one by one for all others. At least with this one, you'll save a little time. All I can say from this point is good luck to you!