Weitlaner was born on April 28, 1883, in Steyr, Austria, the son of the civil engineer Julius Weitlaner and Therese Pillinger, a schoolteacher.
He studied engineering at Montanuniversität Leoben, from which he graduated in 1908 with the degree of metallurgical engineer.
A year later he immigrated to the United States, where he practiced his profession with major American steel companies in Pittsburgh (1909-1910), Buffalo (1910-1913), Philadelphia (1913-1916), Baltimore (1916-1919) and Cleveland (1919-1922).