AirHint found the following cheapest return flights from St. Louis (STL) to London (LGW) in December 2025 (see full year).

Return flights

24 Dec - 17 Jan	Frontier Airlines
23 Dec - 17 Jan	Frontier Airlines
25 Dec - 17 Jan	Frontier Airlines
22 Dec - 17 Jan	Frontier Airlines
30 Dec - 30 Jan	Frontier Airlines
13 Dec - 29 Dec	Frontier Airlines
27 Dec - 17 Jan	Frontier Airlines
15 Dec - 17 Dec	Frontier Airlines
12 Dec - 21 Dec	Frontier Airlines
13 Dec - 21 Dec	Frontier Airlines
11 Dec - 28 Dec	Frontier Airlines
15 Dec - 02 Jan	Frontier Airlines
25 Dec - 01 Jan	Frontier Airlines
29 Dec - 05 Jan	Lufthansa
21 Dec - 04 Jan	Frontier Airlines
14 Dec - 21 Dec	Air Canada

Also check the deals for one-way flights from St. Louis to London 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 London

Cheap car rent in London

Cheapest return flights from St. Louis to London in December from $723

Return flights