Flying from USA search machine

Nikiya

I am trying to buy a round ticket departing from USA for my son. I have been told (and seen) it is a lot more expensive if bought from here.
Some search machines (like viajar.com) have better prices than agencies or OPODO. How reliable are they? and does anybody know a reliable search to travel from USA?
I need to make a quick decision.
THanks so much!

researcher

Not the answer you wanted, but 2 weeks ago my nephew had to get a return flight from the US, where he lives, for a visit to us here. On checking the quotes he was getting there, they were the same as I got here allowing for exchange rates. This was quite surprising but there was no beneficial price difference booking on a US site. I used the 3 sites suggested by Martin.