AirHint found the following cheapest return flights from Denver (DEN) to Istanbul (IST) in December 2025 (see full year).

Return flights

10 Dec - 12 Dec	Frontier Airlines
03 Dec - 15 Dec	Frontier Airlines
05 Dec - 19 Dec	Frontier Airlines
20 Dec - 10 Jan	Turkish Airlines	direct
08 Dec - 22 Dec	Lufthansa
22 Dec - 05 Jan	Frontier Airlines
13 Dec - 23 Dec	Lufthansa
25 Dec - 06 Jan	Turkish Airlines	direct
24 Dec - 05 Jan	Lufthansa
17 Dec - 03 Jan	Frontier Airlines
20 Dec - 06 Jan	jetBlue
23 Dec - 02 Jan	Frontier Airlines
20 Dec - 04 Jan	Frontier Airlines
23 Dec - 02 Jan	Turkish Airlines	direct
19 Dec - 02 Jan	Frontier Airlines

Also check the deals for one-way flights from Denver to Istanbul in December.

The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.

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Cheapest return flights from Denver to Istanbul in December from 623€

Return flights