In February 2022, a US Navy amphibious assault ship—basically, a smallish (250-meter) aircraft carrier—sailed from Pearl Harbor to San Diego without using electronic navigation:
With the approval of the Essex’s commanding officer (CO), Captain Kelly Fletcher, her navigator (coauthor and then–Lieutenant Commander Stanton), and the lead navigation instructor from Surface Warfare Schools Command in Newport, Rhode Island (coauthor Walter O’Donnell), the Essex tested its own proof-of-concept for navigating with a total loss of integrated electronic navigation equipment. Any navigation equipment that used electricity was prohibited, including all GPS sources, the Essex’s electronic Voyage Management System (VMS), and the computer-based celestial navigation software STELLA.
Navy navigators are held to an exacting standard in shiphandling, piloting, seamanship, planning, and ocean sailing. In addition, navigators juggle many administrative tasks, such as department head and senior watch officer duties and preparations for material and administrative inspections. At the same time, The Surface Ship Navigation Department Organization and Regulations Manual (NavDORM) expects that “ships will be prepared to operate in a PNT [position, navigation, and timing] degraded or denied environment.” But a navigator must be always ready and able to do so.
Prior to deployment, Lieutenant Commander Stanton conducted a celestial navigation training series for junior officers and quartermasters of the watch (QMOWs). The series moved from theory to practice, culminating in a hands-on sextant exercise from the Essex’s flying bridge. To ensure the bridge watchstanders could keep a precise and continuous paper plot, Lieutenant Commander Stanton required practice plots during both deployment transoceanic crossings (San Diego to Guam, then Japan to Oahu). The celestial plots, including a continuous plot of dead reckoning positions, were compared directly to GPS, VMS, and STELLA to hone celestial navigation skills while all sensors were still available. For maximum training effect and redundancy, two paper celestial plots were always maintained on the bridge: one by the officer of the deck and the junior officer of the deck, and another by the QMOW.
Twice during the voyage, more than 15 hours elapsed between fixes because of cloud cover. While this length of time may not surprise those who sailed prior to GPS, it is gut-wrenching in today’s Navy after years of easy access to precise, real-time data and communications. Should maintaining a celestial navigation plot become necessary in the future, bridge watch officers and all who rely on their position data will be required to do what has become unnatural at sea—wait.
It's hard to keep fundamentals fresh when modern systems are so much easier. I'd argue that this applies in every kind of art and science. You write more effectively using the fundamental principles of rhetoric and logic; you cook more effectively using fundamental principles of cuisine. (If you don't know what mirepoix is, your sauces and soups won't taste right.)
The Navy knows how fragile global positioning signals can be. The stars don't change on human timescales, though. I hope the Navy makes celestial navigation a required part of navigator training again.