After World War I, he served as the acting head of the RNoNAS's factory until a more senior officer was appointed.

This gave him the opportunity to study the fledgling military and civil aviation infrastructure for which the council was responsible.

Riiser-Larsen agreed and secured the use of two Dornier Do J Wal seaplanes, with Karl Feucht as one of two expedition flight mechanics.

Riiser-Larsen somehow managed to coax the overloaded plane into the air and flew the expedition back to the coast of Northern Svalbard.

[2][3] The following year, Riiser-Larsen rejoined Amundsen for another attempt to fly over the Pole, this time with Italian aeronautical engineer Umberto Nobile in his recently renamed airship, the Norge.

The flight is considered by many to be the first successful overflight or journey of any kind to the North Pole, as the other claimants, Frederick Cook, Robert Peary and Richard Byrd, were unable to verify their attempts in full.

Ostensibly their goal was scientific research and the discovery of new whaling grounds, but Christensen also requested permission from the Norwegian Foreign Office to claim for Norway any uncharted territory that was found.

[7][8] During the Nazi German occupation of Norway, Riiser-Larsen rejoined the Royal Norwegian Navy Air Service.