Santos-Dumont's final flight as a pilot was made in a Demoiselle on 4 January 1910.
The flight ended when a bracing wire snapped at an altitude of about 25 m (80 ft), causing a wing to collapse.
Santos-Dumont suffered only bruises.

In March 1910 Santos-Dumont announced that he was retiring from aviation.
He secluded himself in his house and it was rumoured that he was suffering from a nervous breakdown caused by overwork, but it is probable that he was depressed about the multiple sclerosis from which he was later known to suffer.

In 1911 he moved to the French seaside village of Bénerville (now Benerville-sur-Mer), where he took up astronomy as a hobby.
After the outbreak of war in 1914 his German-made telescope and unusual accent led to accusations he was a German spy tracking French naval activity, and his rooms searched by French police.
Upset by the allegation and depressed about his illness Santos-Dumont burned all his papers and plans.
 For this reason there is little direct information available about his designs today.
He spent much of the 1920s in Swiss and French sanatoria, though returning to Brazil at times.

For his arrival in Brazil on the luxury liner Cap Arcona in 1928, a dozen members of the Brazilian scientific community boarded a seaplane with the intention of paying him a flying welcome.
The plane crashed with the loss of all on board; Santos-Dumont's growing despondency deepened even further, and he returned to Switzerland.
Santos-Dumont's final flight as a pilot was made in a Demoiselle on 4 January 1910. The flight ended when a bracing wire snapped at an altitude of about 25 m (80 ft), causing a wing to collapse. Santos-Dumont suffered only bruises.
In March 1910 Santos-Dumont announced that he was retiring from aviation. He secluded himself in his house and it was rumoured that he was suffering from a nervous breakdown caused by overwork, but it is probable that he was depressed about the multiple sclerosis from which he was later known to suffer.
In 1911 he moved to the French seaside village of Bénerville (now Benerville-sur-Mer), where he took up astronomy as a hobby. After the outbreak of war in 1914 his German-made telescope and unusual accent led to accusations he was a German spy tracking French naval activity, and his rooms searched by French police. Upset by the allegation and depressed about his illness Santos-Dumont burned all his papers and plans.  For this reason there is little direct information available about his designs today. He spent much of the 1920s in Swiss and French sanatoria, though returning to Brazil at times.
For his arrival in Brazil on the luxury liner Cap Arcona in 1928, a dozen members of the Brazilian scientific community boarded a seaplane with the intention of paying him a flying welcome. The plane crashed with the loss of all on board; Santos-Dumont's growing despondency deepened even further, and he returned to Switzerland.
Alberto Santos-Dumont