Some important breakthroughs in site-cast concrete construction are being accomplished in the building of the new parking terminal under construction at the Seattle-Tacoma International Airport. Several design features called for considerable ingenuity on the part of the contractor, as well as innovative sophistication in form construction and handling to make possible the casting of this complex structure swiftly and economically. The prefabricated fiberglass forms being used are said to produce glossy fiberglass forms being used are said to produce glossy, almost glass-like surfaces that require only minimal finishing. All basic parts of the structure are cast-in-place, including the spiral entry and exit ramps. Only the spandrels edging each floor level are of precast concrete. In using fiberglass dome forms to cast the floors, the prime contractor, Peter Kiewit Sons' Company used flying soffits for the temporary supporting structure. These are handled by crane in moving form floor to floor for repeated reuse throughout the project. Use of the fiberglass domes and the flying forms made possible exceptionally rapid form erection for each succeeding floor, at a comparatively low labor cost for what would otherwise have been intricate and time-consuming form work. There are other factors as well that contribute importantly to the speed of completing this complex structure. Circular beams as long as 35 feet are set and stripped as a single unit. Where circular beams intersect the radiating beams, star sections are used for mating and also provide length adjustment. Because the many different shapes and sizes required to meet the 60-plus conditions called for by the design have been built right into the fiberglass forms, on-site working time is reduced to the minimum. Each of these forms can be reused up to 16 times. Central columns and the inner portion of the radial beams are formed using steel units. Weight reduction is a major advantage of the use of domes in a site-cast project of this magnitude. The intersectiong joists formed by the ceiling waffle pattern are 6 feet from center to center, forming voids approximately 5 feet by 5 feet square and 2 feet deep. Total thickness of the floor is 2 feet 4 inches.