Castle Air Force Base Airport (MER) — Atwater, California
Castle Air Force Base Airport, designated by the FAA with identifier MER and carrying the internal reference ID 27525, sits on the grounds of the former Castle Air Force Base in Atwater, Merced County, California. The facility occupies a storied piece of American aviation history, having served as a primary Strategic Air Command (SAC) installation from World War II through the base's closure in 1995. Today the airport operates as a public-use general aviation facility under the management of the Merced County Airport District, preserving and extending the legacy of one of California's most significant military airfields.
The airport is located approximately 7 miles northeast of downtown Merced and sits at an elevation of 191 feet above mean sea level. The facility features two primary runways: Runway 13/31, stretching 11,802 feet, and Runway 5/23, measuring 7,000 feet. The extended length of the primary runway is a direct inheritance from Castle's SAC-era mission, during which Boeing B-52 Stratofortresses required maximum takeoff distance when fully laden with fuel and ordnance. That 11,802-foot strip remains one of the longest publicly accessible general aviation runways in California's Central Valley, making MER an attractive diversion field for larger turboprop and jet aircraft operating in the region.
Atwater itself is a community of roughly 30,000 residents embedded within the agricultural heartland of the San Joaquin Valley. The surrounding Merced County economy centers on dairy farming, almonds, walnuts, and stone fruit production, and the airport plays a supporting role for agricultural aviation operators, crop-dusting services, and charter operators moving passengers and perishable freight across the valley. The presence of the University of California, Merced campus — the newest UC campus, opened in 2005 — approximately 15 miles to the southeast has also contributed modest demand for private aviation connections to the Bay Area and Southern California.
The Castle Air Museum, situated at the airport's perimeter, draws tens of thousands of visitors annually and maintains an outdoor collection of more than 70 historic military aircraft, including a B-52D Stratofortress, a U-2 reconnaissance aircraft, an SR-71 Blackbird, and a rare B-29 Superfortress. This collection, one of the most comprehensive military aviation museums in the western United States, adds cultural and tourism significance to the airport's footprint and reinforces Atwater's identity as a destination tied directly to American airpower heritage.
For pilots operating into and out of MER, the airport provides self-serve 100LL and Jet-A fueling, aircraft tie-down and hangar rental, and a pilot lounge with weather briefing access. The CTAF frequency is 122.8 MHz, and the field operates without an air traffic control tower, requiring standard traffic pattern communications among arriving and departing aircraft. IFR approaches available include GPS/RNAV approaches to both runway configurations, enabling instrument operations during the valley's periodic tule fog events, which can reduce visibility to near-zero from late November through February.
Ground transportation from Castle Air Force Base Airport connects travelers to Atwater city services, Merced's Amtrak station on the San Joaquins corridor, and the broader Highway 99 transportation spine. For those traveling toward the Bay Area, the distance to Livermore Municipal Airport is approximately 75 miles west, while Oakland International Airport — one of the region's primary commercial hubs — lies roughly 100 miles northwest via Interstate 580. The Meadowlark Airport in Livermore and the Direct Airport Shuttle service operating near Oakland International offer additional general aviation and ground connection options for passengers whose itineraries extend beyond Merced County.
Castle Air Force Base Airport (MER) represents the successful adaptive reuse of a military installation, transforming a closed SAC base into a functioning public aviation resource that serves Central Valley agricultural, business, and recreational aviation needs while honoring the base's deep historical and cultural significance to the surrounding community.