AirHint found the following cheapest return flights from London (LHR) to Buenos Aires (AEP) in September 2025 (see full year).

Return flights

25 Sep - 24 Oct	TAP
26 Sep - 06 Oct	TAP
22 Sep - 06 Oct	TAP
11 Sep - 16 Sep	Avianca
14 Sep - 19 Sep	Avianca
08 Sep - 19 Sep	Avianca
08 Sep - 26 Sep	Avianca
16 Sep - 25 Sep	Avianca
02 Sep - 07 Sep	Avianca
11 Sep - 23 Sep	Avianca
03 Sep - 24 Sep	Avianca
01 Sep - 07 Sep	Avianca
15 Sep - 22 Sep	Avianca
15 Sep - 15 Oct	Avianca
11 Sep - 02 Oct	Avianca
30 Sep - 07 Oct	TAP
10 Sep - 12 Oct	TAP
16 Sep - 14 Oct	Avianca
17 Sep - 14 Oct	TAP
10 Sep - 13 Oct	LATAM Airlines Group

Also check the deals for one-way flights from London to Buenos Aires 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 London to Buenos Aires in September from 876€

Return flights