Budd based the Amfleet design on its earlier Metroliner electric multiple unit.

An initial order for 57 cars in 1973 to supplement the Metroliners on the Northeast Corridor grew to two orders totaling 642 cars, sufficient to reequip all the services on the Northeast Corridor and many other routes around the United States.

As of 2023[update], Amfleet cars are used extensively in the eastern and midwestern United States, forming the backbone of Amtrak's single-level fleet, with 580 out of the original 642 in service as of October 1, 2023.

[2] Amtrak assumed control of almost all private sector intercity passenger rail service in the United States on May 1, 1971, with a mandate to reverse decades of decline.

[3] To operate these trains, Amtrak inherited a fleet of 300 locomotives (electric and diesel) and 1190 passenger cars, most of which dated from the 1940s–1950s.

This fleet of 61 cars had begun operation between Washington, D.C., and New York City on the Northeast Corridor in 1969 under Penn Central and quickly gained acceptance with the traveling public, despite various engineering problems.

[8] Amtrak placed a $24 million order with Budd on October 12, 1973, for 57 "non-powered Metroliner cars."

These, together with new GE E60 electric locomotives, were to provide additional Metroliner service on the Northeast Corridor.

[11] Finally, in April 1975, with the first deliveries imminent, Amtrak added 200 more cars to the order for $86 million.

[14] A public unveiling took place at the Budd plant in Northeast Philadelphia on June 19, 1975, after which four cars were sent to the High Speed Ground Test Center in Pueblo, Colorado, for evaluation.

"[5] A 1978 study conducted by the Federal Railroad Administration (FRA) found that ridership increased 11% on the Amfleet-equipped Northeast Corridor trains, with at least some passengers choosing the slower but more comfortable Amfleets over the faster but less reliable Metroliners.

[16] The rollout of Amfleets throughout the system was restricted by the availability of locomotives with HEP or special generator cars.

Besides the Blue Ridge, routes using Amfleets outside the Northeast Corridor included the New York–Newport News, Virginia Colonial, the Chicago, Illinois–Detroit, Michigan Twilight Limited and Wolverine, the Chicago–St.

Louis, Missouri Abraham Lincoln and State House, the Chicago–Quincy, Illinois Illinois Zephyr, the Chicago–Carbondale, Illinois Illini and Shawnee, the Chicago–Dubuque, Iowa Black Hawk, the Los Angeles–Bakersfield, California San Joaquin, the Los Angeles–San Diego, California San Diegan, the Portland, Oregon–Seattle, Washington Mount Rainier and Puget Sound, and the Seattle–Vancouver, British Columbia Pacific International.

[19] The Amfleet's modern HEP system proved invaluable during the unusually harsh winter of 1976–1977, which sidelined many of Amtrak's aging steam-heated coaches.

Amtrak suspended numerous routes and pressed the short-distance Amfleet I coaches into long-distance service.

[22] These cars, dubbed Amfleet II, were intended to replace rolling stock on Amtrak long-distance trains, and featured larger windows, more legroom, and folding legrests.

[27] The Superliner II order in the early 1990s would lead to the removal of Amfleets from the Auto Train and Capitol Limited.

[33] The following year, Amtrak began to investigate options to replace the Amfleet I cars altogether.

[37] By February 2021, Amtrak planned for the replacements to be trainsets rather than individual cars, with options for diesel, electric, or dual-mode propulsion.

Siemens was announced as the preferred bidder in April 2021, with contract execution for 83 trainsets expected midyear.

[42] Procurement for a new overnight fleet, including possible replacement of the Amfleet II cars, began in 2022.

[32] Electric heating and air conditioning, operated by head-end power (HEP) from the locomotive, are used to maintain passenger comfort.

[44] Reinforcing the impression of traveling in an airliner, the passenger seats themselves were built by the Amirail division of Aircraft Mechanics Inc.[53] Cesar Vergara, head of car design at Amtrak in the 1990s, criticized the choice to copy the airliner aesthetic:[54] Amfleet is a totally American style that was meant to imitate airplanes.

[57] Amfleet seats have swing-down tray-tables for at-seat food service, as well as overhead and underseat luggage storage.

During the 1980s most of the Amfleet I long-distance coaches were refurbished for use on the premium Metroliner service on the Northeast Corridor.

[25] By the 2010s all the remaining dinettes were rebuilt with all-table seating, save two which were converted into short-distance coaches.

Most clubs were rebuilt as club-dinette cars, with one half given over to booths and the other having 2×1 business class seating.