It's an all-out fare war on flights to Europe among the "Big 3" airline alliances associated with American, Delta, and United. Along with great fares to Western European cities, we're seeing amazing prices for flights to Eastern Europe in the $400s roundtrip from several U.S. cities.
Best of all, some of these flight deals are booking into regular Economy, which means one free checked bag is included and you'll be able to choose your seat assignments. Read the details when booking because most of the deals book into Basic Economy.
We rarely see prices drop this low from smaller hub cities like Atlanta (ATL), Detroit (DTW), Denver (DEN), Cincinnati (CVG), Cleveland (CLE), Houston (IAH), Minneapolis (MSP), and Salt Lake City (SLC).
Some flights may be operated by airline partners such as Air Canada, Air France, British Airways, Iberia, KLM, Lufthansa, or Swiss. Who knows how long these deals will stick around. I'd suggest booking right away if you see something you like.
Travel from late October through early April. The lowest fares are available for travel to Europe Sundays through Wednesdays, returning from Europe Tuesdays through Fridays. It may be only slightly more expensive to travel on the weekends.
Peak holiday travel times in late December and early January are blacked out, though you may find availability over New Year's if you stay through the first week of January.
This sale is unadvertised and fares may jump at any moment. Try many different sites if you are finding prices jumping as inventory may still be available on another booking engine.
Cincinnati to Helsinki $447 roundtrip
Cincinnati to Zagreb $456 roundtrip
Atlanta to Brussels $458 roundtrip
Detroit to Amsterdam $459 roundtrip
Atlanta to Milan $462 roundtrip
Washington D.C. to Warsaw $475 roundtrip
Atlanta to Sofia $478 roundtrip
Detroit to Krakow $479 roundtrip
Atlanta to Ljubjana $480 roundtrip
Detroit to Prague $483 roundtrip
Washington D.C. to Helsinki $483 roundtrip
Atlanta to Nice $485 roundtrip
Minneapolis to Rome $488 roundtrip
Atlanta to Athens $489 roundtrip
Detroit to Athens $489 roundtrip
Minneapolis to Athens $490 roundtrip
Salt Lake City to Paris $490 roundtrip
Houston to Athens $493 roundtrip
Cincinnati to Bucharest $493 roundtrip
Atlanta to Budapest $495 roundtrip
Minneapolis to Warsaw $495 roundtrip
Cincinnati to Prague $495 roundtrip
Detroit to Budapest $496 roundtrip
Detroit to Venice $496 roundtrip
Detroit to Sofia $497 roundtrip
Minneapolis to Lyon $498 roundtrip
Salt Lake City to Prague $498 roundtrip
Atlanta to Bucharest $499 roundtrip
Detroit to Berlin $502 roundtrip
San Francisco to Athens $505 roundtrip
Minneapolis to Zagreb $520 roundtrip
Denver to Budapest $522 roundtrip
Denver to Bucharest $528 roundtrip
Washington D.C. to Sofia $533 roundtrip
Cleveland to Prague $545 roundtrip
Salt Lake City to Ljubjana $546 roundtrip
Houston to Zagreb $574 roundtrip
Some of these fares are standard Main Cabin Economy fares, which include one free checked bag. Basic Economy fares only include a carry-on bag plus one personal item and the first checked piece of luggage will cost $60 each-way. On some routes, it could be the same price to upgrade to a Main Cabin Economy fare.
Main Cabin Economy fares include advanced seat assignments. Seats will be assigned at random upon check-in for Basic Economy. You may be able to pay a fee to choose a specific seat.
Related: Today's Best Flight Deals to Europe
Upgrading from a Basic Economy fare to a standard Main Cabin Economy fare will cost an additional $120-$180 on most routes. Certain travel dates and/or routes may be much more to upgrade. This type of fare will include one free checked bag, seat selection, and are eligible for upgrades/ticket changes (fee applies).
Some of the prices listed require two stops and it may only be slightly more expensive to fly on a different carrier or routing with only one stop.
As an example, I found seats in standard Economy departing Atlanta ATL on Wednesday, November 13, with a return flight from Ljubljana LJU on Thursday, November 21, for $482 roundtrip. That includes one free checked bag!