A British satellite company has solved one crucial aspect of the mystery surrounding the Malaysia Airlines flight that disappeared on March 8, using a complex mathematical process to determine that it ended its journey in the middle of the southern Indian Ocean.

Guided by a principle of physics called the Doppler effect, the company, Inmarsat, analyzed tiny shifts in the frequency of the plane’s signals to infer the plane’s flight path and likely final location. The method had never before been used to investigate an air disaster, officials said.

The first definitive news of the fate of the Boeing 777 jet brought heartbreak to the families of those on board as Malaysia’s prime minister, Najib Razak, announced on Monday that no one is believed to have survived the flight.