NASA's P-3 Orion, a former Navy patrol plane modified into a "flying lab".
The Argentine Navy began a search on Friday, November 17, for the submarine San Juan after contact with it was lost two days previously. The P-3 is equipped with a magnetic anomaly detector (or magnetometer), a gravimeter for detecting small fluctuations in the Earth's gravity, infrared cameras, and other sensors for measuring ice thickness.
Submarines often ply the Argentine coast to detect illegal fishing.
The P-3 had been flying out of the Argentine city of Ushuaia as part of NASA's IceBridge annual Antarctic survey.
Steve Ganyard, an ABC News contributor and a former deputy assistant secretary of state, said the San Juan was almost 35 years old but had undergone a "midlife upgrade" in 2013.
"We are investigating the reasons for the lack of communication", said Enrique Balbi, a naval spokesman, according to Reuters.
The United States, Britain and Canada have offered to help Argentina locate the missing vessel with boats and satellites.
Officials also said aircraft and ships are searching in the area of the submarine's last known position.
Argentina's navy launched a huge search and rescue operation to discover the missing submarine.