Santos embarked on an ambitious development programme after this modest triumph, and soon became a familiar sight puttering over the Paris suburb of Neuilly-Saint James on his latest dirigible. In the summer of 1901 he made two attempts to win a 125,000-franc prize offered by Henri Deutsche de la Meurthe for a flight from the parc d’aerostation at St Cloud to the Eiffel Tower and back, a distance of about 12 km (4 miles), in half an hour. The first began on 13 July. With a following wind Santos’s No. 5 dirigible was soon rounding the Eiffel Tower, but on his return trip the little air-ship could make no headway, the time limit elapsed and the engine stopped. Santos valved off hydrogen and settled into a large chestnut tree in the grounds of Edmund de Rothschild’s house. During his second attempt, on 8 August, Santos again circled the Eiffel Tower but was foiled on the way back, crashing noisily and explosively on to the roof of an hotel at Trocadéro. Shaken and singed he climbed through an attic window and was held by the manager on suspicion of cat burglary.
Another dirigible was hastily constructed to replace the wrecked No. 5, and on 19 October 1901 Santos just succeeded in making the round trip within the specified 30 minutes. Typically philanthropic, he divided the prize between his workers and the Parisian poor, keeping not a centime for himself.