AirHint found the following cheapest return flights from Raleigh-durham (RDU) to Lisbon (LIS) in September 2025 (see full year).

Return flights

08 Sep - 15 Sep	Spirit Airlines
17 Sep - 27 Sep	Frontier Airlines
30 Sep - 07 Oct	United
24 Sep - 01 Oct	United
09 Sep - 16 Sep	United
03 Sep - 10 Sep	United
27 Sep - 04 Oct	United
15 Sep - 22 Sep	United
11 Sep - 18 Sep	United
04 Sep - 08 Sep	United
13 Sep - 20 Sep	United
05 Sep - 12 Sep	United
19 Sep - 26 Sep	United

Also check the deals for one-way flights from Raleigh-durham 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 Raleigh-durham to Lisbon in September from 540€

Return flights