The Japanese Occupation Army sent Aalbers and his family to the Dutch intern camp in Cimahi and then were transferred to the Jatinegara camp in Jakarta.
He was a town planning consultant for Semarang (1916–20, 1936), Buitenzorg (now 'Bogor') (1920–23), Madiun (1929), Malang (1930–35), Batavia (Jakarta) (1936–37), Magelang (1937–38), Bandung (1941), as well as Cirebon, Meester Cornelis (part of Jakarta which is known as Jatinegara), Yogyakarta, Surakarta, Purwokerto, Padang, Medan and Banjarmasin.