The R44 fleet originally consisted of 352 cars, of which 56 remain in service, all on the Staten Island Railway.

The first R44 cars entered service on the subway on April 19, 1972, and on the Staten Island Railway on February 28, 1973.

The R44s had orange and yellow plastic bucket seats—a feature that would be incorporated into the other 75-foot (22.86 m) B-division cars and the A-division R62s and R62As.

The R44 was the first car since the BMT Green Hornet to incorporate a two-note warning tone, the first two notes of Westminster Quarters, that sounds before the doors begin to close as the train prepares to leave the station.

[citation needed] When the cars were built, the chime was sounded four seconds before the doors closed, but the time delay was later removed.

[citation needed] The rollsigns from eight R44s were removed and replaced by experimental flip-dot signs starting in 1988, the same year the New Technology Program began.

The cars were capable of attaining even higher speeds, but the length of the test track was insufficient to allow further acceleration.

[7] After many months of exhaustive testing on the A, D, E, and F (one week on each service, starting December 16, 1971), as well as on the LIRR to test the cars' state-of-the-art electrical and mechanical systems, the first set of R44s was placed in service on the New York City Subway on the F on April 19, 1972, following a brief introductory ceremony attended by the Mayor of New York City John V. Lindsay, along with MTA Chairman William J. Ronan at Jamaica–179th Street station.

Cars 5282–5285 were involved in a derailment north of 135th Street, resulting in the whole set being placed out of service.

All SIR cars were overhauled for a second time between 2007 and 2010 as a part of scheduled maintenance program.

Several improvements included the repainting of the bulkheads, rebuilt trucks, new dark floors, newly repainted periwinkle bucket seats, and updated logos; unlike the NYCT cars, the SIR cars retained their original blue "M" MTA decals during their first overhaul.

[10] The cars have been undergoing further intermittent rounds of scheduled maintenance as their parts age over time.

On December 26, 2008, car 402 was pulled from service after being badly damaged from accidentally hitting a bumper block at the Tottenville station.

[25] On December 18, 2009, two 4-car sets of New York City Transit R44s, one set being a contract Morrison-Knudsen rebuild and the other being an in-house Coney Island Overhaul Shop rebuild, were brought in to the 207th Street Overhaul Shop for inspection; the inspection resulted in various structural integrity issues being discovered on all eight cars.

Car 5344, part of one of the sets brought in for inspection, was the first to be completely stripped in preparation for disposal as an artificial reef.

Since January 2022, the remaining R44s have been the oldest active rolling stock within the NYCT system at 51 years old, following the retirement of the R32s.

As such, the SIR R44s not written off received intermittent rounds of scheduled maintenance to extend their usefulness until retirement.

[26][32] Ultimately, 75 R211S cars have been ordered to replace the SIR R44s; these started entering service on October 8, 2024.