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

Return flights

23 Sep - 03 Oct	Avianca
23 Sep - 05 Oct	Avianca
23 Sep - 02 Oct	Avianca
26 Sep - 03 Oct	Avianca
26 Sep - 02 Oct	Avianca
24 Sep - 15 Oct	Avianca
23 Sep - 26 Sep	Avianca
22 Sep - 28 Sep	Avianca
24 Sep - 28 Sep	Avianca
26 Sep - 12 Oct	Avianca
26 Sep - 25 Oct	Avianca
25 Sep - 18 Oct	Avianca
22 Sep - 25 Sep	Avianca
27 Sep - 04 Oct	Avianca
25 Sep - 30 Sep	Avianca
22 Sep - 26 Sep	Avianca
22 Sep - 27 Sep	Avianca
27 Sep - 30 Sep	LATAM Airlines Group
26 Sep - 28 Sep	Avianca
26 Sep - 30 Sep	Avianca

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 874€

Return flights