AirHint found the following cheapest return flights from Knoxville (TYS) to Washington (IAD) in December 2025 (see full year).

Return flights

11 Dec - 18 Dec	Allegiant Air	direct
27 Dec - 08 Jan	Allegiant Air	direct
11 Dec - 24 Dec	Allegiant Air	direct
26 Dec - 29 Dec	United	direct
19 Dec - 21 Dec	United	direct
12 Dec - 14 Dec	Allegiant Air
16 Dec - 22 Dec	United	direct
12 Dec - 14 Dec	United	direct
10 Dec - 11 Dec	Allegiant Air
10 Dec - 11 Dec	United	direct

Also check the deals for one-way flights from Knoxville to Washington 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.

Book a cheap hotel in Washington

Cheap car rent in Washington

Cheapest return flights from Knoxville to Washington in December from $130

Return flights