Rainer Schaller -- who owns Gold's Gym, among other brands -- is missing alongside his family after their plane disappeared overnight ... with officials all but confirming they're dead.
A private plane carrying Schaller, his partner Christiane Schikorsky, their children and a reported fitness trainer are listed as the five passengers who have gone unaccounted for since their aircraft vanished off the Costa Rican coast while traveling from Mexico Friday.
Reports say the plane lost all communication with a control tower while it was flying near Barra del Parismina in the Caribbean Sea -- and now, the Costa Rican Coast Guard is saying they've found several pieces from what they believe is the wreckage, including at least 2 bodies.
The identities of the two corpses have not officially been announced just yet, but some reports say Costa Rican officials are declaring Schaller among 6 people (pilot included) that are presumed dead at this point. A search is still underway to find the others ... some personal belongings, like luggage, have been retrieved in the open sea though.
Schaller is the founder and CEO of the RSG Group -- which runs and operates a string of gym chains across the world, including McFit, John Reed and of course ... Gold's, which he acquired a couple years ago after it filed for bankruptcy in the pandemic.