Loewenstein made an enormous fortune providing electric power facilities for developing countries worldwide through his Belgian-based company, Société Internationale d'Énergie Hydro-Électrique (SIDRO).

In 1926, Loewenstein established "International Holdings and Investments Limited", which raised huge amounts of capital from wealthy investors wishing to get aboard his bandwagon of success.

In 1926, he bought Villa Sacchino, a sumptuous house in Biarritz, in the French Basque Country, with a view on the Bay of Biscay and the Atlantic Ocean.

On the evening of 4 July 1928, Loewenstein left from Croydon Airport to fly to Brussels on his private aircraft, a Fokker F.VIIa/3m trimotor (G-EBYI), along with six other people.

[5][6] When Loewenstein had not reappeared after some time, his secretary went in search of him and discovered that the lavatory was empty, while the aircraft's entrance door was open and flapping in the slipstream.

[7][6] News of Loewenstein's demise caused panic selling in his corporations' publicly traded shares, which immediately plummeted in value by more than fifty percent.

The New York Times hypothesised that a growing absent-mindedness, noted by many of Loewenstein's acquaintances, may have caused him to walk out the wrong door of the aircraft.

He also shows that later events are frequently ignored, such as the fact that Loewenstein's son Robert shot one of the family servants under murky circumstances within a decade or so after the tragedy.

Crime writers Robert and Carol Bridgestock have speculated that Loewenstein faked his own death and disappeared because of the financial irregularities in his businesses.