Book 6-8 weeks ahead for the best fares on the FRA to DEN route.
Tuesday and Wednesday departures are typically 15-20% cheaper.
This is a long-haul flight (~9h 31m). Consider comfort upgrades or stopover options.
Compare 2 airlines on this route: LH, UA.
Check visa requirements for your destination well in advance.

Route details All flights from FRA All flights from DEN