While in regular service, each R33S was coupled to five two-car consists of R36 cars to make 11-car trains for the 7 and <7> routes.

The R33S fleet entered service on September 26, 1963, and was originally painted in a light blue turquoise "Bluebird" scheme.

The Redbirds were painted between 1984 and 1989 to a deep maroon red body, black front bonnets and anti-climbers, and a silver roof.

[3] The cars were solely assigned to the 7 (IRT Flushing Line) and were based out of Corona Yard.

However, they were not retrofitted with air conditioning system and instead retained their original Axiflow ceiling fans.

While the Redbirds on the IRT Main Line were beginning to be retired starting in early 2001, the 7 service was still provided by R33S and R36 cars.

Car 9339 was retired, stripped, and then sunken as an artificial reef in 2010 after it suffered fire damage that year.