In 1921, Dahl was admitted as a student at the Army Flyvevæsens flight school at Kjeller in Skedsmo where he received an international pilot's license.

Roald Amundsen hired him in 1922 as a pilot, mechanic, radio operator and cinematographer on an expedition in the Arctic Ocean in an effort to fly over the North Pole.

One of Dahl's main tasks were to take observations and maintain and construct instruments for the expedition's scientific director, Harald Sverdrup, who at the time was employed at The Carnegie Institution of Washington.

[2][3] After a year at the Carnegie Institution, he became involved in developing devices for high voltages for use in nuclear physics, an area where the United States at that time was lagging behind Europe.

In the early stages of CERN, Dahl was invited to participate and finally in 1952 to lead the Proton Synchrotron Group's work, to which his contribution had a definitive role.