Built in 1938 (with WPA funds), this large Seaplane Hangar provided shelter for Navy seaplanes. It was sited near the Pontiac Bay at the north end of the naval air station and to Building 2 for proximity to the plane assembly and repair facility. In more recent years, Building 27 has been used for aircraft repair, offices, and heavy equipment storage. Currently the building is vacant with adaptive re-use plans for indoor participation sports.