AirHint found the following cheapest return flights from Atlanta (ATL) to Lisbon (LIS) in September 2025 (see full year).

Return flights

23 Sep - 07 Oct	Spirit Airlines
30 Sep - 08 Oct	Turkish Airlines
16 Sep - 23 Sep	Turkish Airlines
26 Sep - 05 Oct	Frontier Airlines
16 Sep - 11 Oct	Turkish Airlines
29 Sep - 09 Oct	United
22 Sep - 18 Oct	Frontier Airlines
12 Sep - 18 Sep	Frontier Airlines
11 Sep - 18 Sep	Frontier Airlines
26 Sep - 03 Oct	Frontier Airlines
13 Sep - 04 Oct	Spirit Airlines
24 Sep - 28 Sep	Spirit Airlines
12 Sep - 04 Oct	Frontier Airlines
09 Sep - 16 Sep	Spirit Airlines
14 Sep - 04 Oct	Frontier Airlines
14 Sep - 19 Sep	TAP

Also check the deals for one-way flights from Atlanta to Lisbon in September.

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 Lisbon

Cheap car rent in Lisbon

Cheapest return flights from Atlanta to Lisbon in September from $577

Return flights