Jan Koum's Gulfstream G650ER lands at Rijeka, 36 nm from where his yacht Mogambo is anchored

The timing would also fit a broader pattern of Adriatic activity. Recent flights by the same owner show a September 13 movement from the Paris area to a point off the Croatian coast, and an August 20 hop from Teterboro to the region, per tracking data. The Kvarner Gulf, where Rijeka sits, is a known summer cruising ground for superyachts, and the presence of four owned vessels within roughly 50 nautical miles suggests a planned rendezvous rather than a coincidence. No specific event—no regatta, no film festival, no business conference—was reported in Rijeka this week in local or international media, so the most grounded explanation is a private gathering of the fleet, perhaps to reposition for the autumn season or to enjoy the last of the Mediterranean weather.

Jan Koum's aviation and maritime habits have long favored the Mediterranean corridor. His homes include a château in Cap d'Antibes, and his aircraft have repeatedly flown between the U.S. East Coast, the UAE, and southern France, per tracked flights. The short Zadar-to-Rijeka leg, sandwiched between longer international hops, reads as a final positioning move—if aboard, Jan Koum would be consolidating his assets in one of his preferred corners of the Adriatic, with the yacht fleet as the likely anchor. As always, the flight is the fact; the passenger remains the inference.

For a man who built WhatsApp and left Facebook over privacy disputes, the appeal of a quiet anchorage over a conference hall is hardly surprising. The jet did its part; the rest is the sea's business.