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

Return flights

03 Sep - 10 Sep	Spirit Airlines
10 Sep - 18 Sep	Spirit Airlines
01 Sep - 30 Sep	Spirit Airlines
08 Sep - 15 Sep	United
10 Sep - 17 Sep	United
16 Sep - 23 Sep	United
30 Sep - 07 Oct	United
06 Sep - 13 Sep	United
26 Sep - 03 Oct	United
18 Sep - 25 Sep	United
24 Sep - 01 Oct	United
22 Sep - 29 Sep	United
12 Sep - 19 Sep	United

Also check the deals for one-way flights from Indianapolis 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.

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Cheapest return flights from Indianapolis to Lisbon in September from 581€

Return flights