Where can I find discount airfare from U.S. to Europe?

Looking to go to Portugal over the summer.
discount airfare europe.

MadMan:On any of the travel websites. No one site always has all the cheapest deals. Try www.Kayak.com to compare sites.

CARLOS O:Please check:
Tips:
a- use flexible dates
b- use alternative airports

http://www.hotwire.com/

http://www.cheapoair.com/

http://www.kayak.com/

http://www.orbitz.com/

http://www.priceline.com/

http://www.expedia.com/default.asp

http://www.farecompare.com/

http://www.farecast.com/

http://www.airfarewatchdog.com/

http://www.cheapair.com/

mega,bus:guess this person must think there is ONLY ONE Airport
FOR THE ENTIRE US!
otherwise hey would have told us the city
must have played too much hookey from school