Teniente Abundio Cesteros García served in 5-E-3/3-E-3 and 8-E-3 during the Spanish Civil War.

On 16 June 1938, the pilots of the first fighter course held in the Nationalist zone were graduated. The large number of accidents caused by new and inexperienced Fiat pilots in December and January had showed that it was essential to set up a school of this type.
Gallur was chosen as the aerodrome and Maggiore Guido Nobili and teniente Ramón Senra Àlvarez (from Group 2-G-3), were posted there as instructors.
The first fighter course lasted for two months and was attended by 22 pupils. Of these, six were sent to 2-G-3 (José Luis Bernal de Mérida, José M.^a Etayo Elizondo, Luis Alcocer Moreno Abellá, Antonio Manrique Garrido, Cesteros and Diego Vigueras), eight to 3-G-3 (Heraclio Gautier Larrainzar, Enrique Munaiz de Brea, Fernando Arrechea Belzunce, Carracido, Acuña, Alonso Fariña, P. Téllez Rivas and Epelde), and of the remainder four were posted to fly He 51s, three to the He 45s and one to the Aero 101s.

On 5 July 1938, a patrol formed by capitán Ángel Salas, Isidro Comas Altadill and Cesteros took off to seek out enemy aircraft operating over the Villel front, to the south of Teruel. Anti-aircraft fire indicated the position of an enemy formation and, closing gradually, Comas Altadill and Cesteros each claimed an I-16.
Flying over the Teruel front, capitán Eduardo Claudín Moncada, CO Grupo N^o 21 (I-16), perished when his Mosca reportedly was hit by Nationalist anti-aircraft fire and crashed in enemy-held territory near Villaestar.
His posthumous promotion to mayor was dated 7 July 1938.
Claudín was replaced by Manuel Zarauza Clavero as CO Grupo N^o 21. His appointment was dated 23 July 1938, and he remained in this position until the fall of Catalonia four months later. Zarauza usually flew Mosca ‘CM-225’, which was assigned to the grupo staff.

Cesteros ended the Spanish Civil War with 5 victories and 1 probable while flying the Fiat CR.32.

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1938
1	05/07/38		1	I-16 (a)	Destroyed	CR.32		Villel front	1-E-3
2	??/??/3?		1	Enemy aircraft	Destroyed	CR.32		Spain
3	??/??/3?		1	Enemy aircraft	Destroyed	CR.32		Spain
4	??/??/3?		1	Enemy aircraft	Destroyed	CR.32		Spain
5	??/??/3?		1	Enemy aircraft	Destroyed	CR.32		Spain
	??/??/3?		1	Enemy aircraft	Probably destroyed	CR.32		Spain

Biplane victories: 5 destroyed, 1 probably destroyed.
TOTAL: 5 destroyed, 1 probably destroyed.
(a) Nationalist pilots claimed 2 I-16s but only 1 I-16 seems to have been lost.

Sources:
Air War over Spain - Jesus Salas Larrazabal, 1974 Ian Allan Ltd, Shepperton, Surrey, ISBN 0-7110-0521-4
Fiat CR.32 Aces of the Spanish Civil War - Alfredo Logoluso, 2010 Osprey Publishing, Oxford, ISBN 978-1-84603-983-6
Additional information kindly provided by Alfredo Logoluso and Ondrej Repka.