King Juan Carlos, who recently underwent hip surgery, was notably not present for the Fiesta Nacional military parade in Madrid.
Prince Felipe, who is playing an increasingly visible role, presided over the Saturday event, along with his wife Princess Letizia.
Queen Sofia and Infanta Elena joined them later for a reception at the Royal Palace.
The Prince of Asturias stepping in for his father more and more has led to news outlets and politicians to suggest changes in the Constitution or at least Spanish law to give the Prince more of an official role.
The King and his son did meet with Prime Minister Mariano Rajoy and other officials at Zarzuela Palace today to discuss the upcoming Ibero-American Summit.
The Prince, because he is not a head of state or government, will not be able to step in for his father to lead the Spanish delegation. Instead he will host associated events.
Also in recent days, Queen Sofia celebrated her brother in law Carlos Zurita, the Duke of Soria, who heads a booster group for the famed Prado museum.
And in the ongoing saga over the corruption investigation plaguing the King’s son on law, Infanta Cristina’s husband, El País reported that their Barcelona home is on sale to make bond.
In recent days news outlets have been reporting about leaked information about the couple’s expenses, including shrimp fajitas at a Washington, D.C. area restaurant.