Deliveries to reconnaissance units of the Breguet 521 began in 1935.
Battle of France
Only a few of the Breguet 521s remained when the Battle of France started in May 1940.
The remaining Breguet 521s were taken over by the Germans and used in air-sea rescue.
Free French Use
One of the Breguet 521s was recaptured by the Free French forces in 1944.