The Military Easter on January 6th was attended by King Felipe and Queen Letizia, along with Princess Leonor, but many wondered where Sofia was.
The Infanta was still in Spain before returning to Lisbon to continue her university studies, so her absence was not due to being abroad.
The reason is much simpler and relates to the historical protocol of this act. Since the 18th century, the Military Easter has been reserved for the Head of State and the military chain of command.
This means that only monarchs and the heir to the throne attend. Sofia doesn’t have that condition, so her absence is completely justified.
However, there was one instance where this rule was broken. It was 25 years ago, in 2001, that Princesses Elena and Cristina appeared at the event with their husbands.
Juan Carlos I delivered a speech explaining that Easter coincided with the 25th anniversary of his reign, and he wanted the entire Royal Family to express their affection and appreciation for the Armed Forces. It was a one-time exception for a very special occasion.
Since then, the format has returned to normal, with only the monarchs and the heir present, who at that time was Felipe and is now Leonor.
Sofia’s absence is not related to her not undergoing military training like her sister. Even if she were to pursue military training in the future, she would still not attend the Military Easter because the criterion for attendance is not training, but her status as heir to the Crown.
Leonor is there because she is the Princess of Asturias, not because she attends the Military Academy. The difference between the two sisters at this event is not a matter of preparation or closeness to the institution, but rather their constitutional roles.