Denver fares in $440s to $470s are available to Paris, Amsterdam and Brussels with American Airlines/Oneworld, United/Star Alliance and Delta/SkyTeam. Manchester UK is also in upper $400s. looks to be the most western U.S. airport with low fares still around this weekend to Europe. Frankfurt, Munich and London are low to mid-$500s.
The links below list American, Delta and United, but some of these low fares are alliance partner tickets.
Departure dates are generally Jan 9 to May 10 with more limited range of dates for some destinations.
Amsterdam, Netherlands (lowest fares Feb 25-May 10)
American $452 Jan 9 – May 10
Delta $448 Jan 9 – May 10
United $445 Jan 8 – May 10
Paris, France
American $444 Jan 8-May 10
Brussels, Belgium
American $483 Feb 25 – Mar 31
Delta $456 Feb 25 – Mar 31
United $442 Feb 25 – Mar 31
Manchester, UK
American $484 Jan 10 – Mar 29
Frankfurt, Germany
American $545 Jan 8 – Mar 31
Delta $548 Jan 8 – Mar 31
United $533 Jan 8 – Mar 31
Munich, Germany
American $552 Feb 25 – March 31
Delta $552 limited dates
London, UK
American $583 Jan 9 – May 10
British Airways Denver – London LHR – Paris CDG – Dallas DFW – Denver
$463.52 round trip Sat Mar 11 – Mon Mar 20
Lufthansa Airlines Denver – Munich – Amsterdam – Washington IAD – Denver
$478.34 round trip Sat May 6 – Sun May 14
Loyalty Traveler curated Airfare Deals and Google Flights and Kayak Explore tutorials.