solely assigned to the (IRT Flushing Line) and were based out of Corona Yard. The cars were rebuilt in-house in 1985 by the Coney Island Shop, except for one car (9306), which was not rebuilt and instead sent to the New York Transit Museum in 1976. However, they were not retrofitted with air conditioning system and instead retained their original Axiflow ceiling fans. For this reason, they were not used during the summer months due to poor air circulation or air flow and high humidity; the 7 train used 10 car trains when the cars were not used. Retirement and after-life service In 1996, New York City Transit Authority announced their plan to phase out the Redbirds with the R142 and R142A fleets. While the Redbirds on the IRT Main Line were beginning to be retired starting in early 2001, the service was still provided by R33S and R36 cars. In January 2002, a set of R62As arrived from the IRT mainline. As more R142s and R142As were delivered, R62As were gradually transferred from the and to the , in turn replacing R33S/R36 trains. The last car remaining R33S, 9309, made its final trip on November 3, 2003, on the 7 service with ten R36 cars, marking the end of the Redbirds and non-stainless steel cars in the subway. Most R33S cars were converted to work motors in the early 2000s, and handle such tasks as providing traction for B-Division rail adhesion cars and refuse trains. The number "1" was placed before the former number (i.e. car 9345 became 19345) of some cars. The work cars are based out of various yards around the system and handle such tasks as providing traction for A-Division rail adhesion cars and refuse trains, and hauling cars during car moves between different subway yards. The cars that were not converted were 9306 and 9327, which were preserved as heritage cars after their retirement from revenue service, and 9321, which was stripped and sunken as an artificial reef in 2001. Recently, the remaining R33S cars have been decommissioned as they experience structural or mechanical issues. Car 9339 was retired, stripped, and then sunken as an artificial reef in 2010 after it suffered fire damage that year. A handful of cars were replaced by reassigned R32 cars, stripped of parts to keep other IRT SMEE cars running, and then scrapped in 2013. Four cars were sidelined