After another update in 1974, very few changes were made until 1992, when again Lester Associates was hired to update the model to coincide with the re-opening of the museum, after a two-year total renovation of the building by Rafael Viñoly. The model makers changed over 60,000 structures to bring it up-to-date at that time. There are now 895,000 structures total, including buildings made of plastic or wood. There are also bridges made of brass. The mechanical "helicopter" vehicles for conveying exhibition visitors were showing signs of wear, and were removed before the 1994 reopening. The current installation by Viñoly features accessible ramps and an elevated walkway which surround the Panorama, allowing viewers to proceed at their own pace, or to linger for as long a look as they desire. Because of space constraints, portions of the walkway are cantilevered over the outer edges of the map, but a glass floor still allows views of the model below. As in the original installation, tiny scale model airplanes take off and land at the model airport of LaGuardia Airport, mechanically guided by long wires.