Arne Alexander Wilhelmsen has offloaded $78.5m in shares of Royal Caribbean Group, which was co-founded by his late father.

The company board member sold 278,720 common shares on Monday at $94.56 each and another 442,894 shares on Tuesday at $95.22 each, according to a US Securities and Exchange Commission (SEC) document.

The two sales tranches leave Wilhelmsen with 14,509 directly...