American, United, Air Canada, Lufthansa (a few) have round trip airfares travelling from Denver (DEN) to Paris France (CDG) for $441, making 1 stop. The stops with American or United is shorter than if it were on Air Canada.
Travel Availability: good availability mid-January thru first week of March 2018
Book this on Priceline [priceline.com]
using dates from that time frame. Click "flexible dates" to return choices, if you're flexible. Bundling hotel with airfare will save you money.
link to recent travel deals