In 1991, the company became a subsidiary of Navistar International, leading to a series of acquisitions of school bus body manufacturers by chassis suppliers during the 1990s.

By the beginning of the 1980s, the last of the generation had completed their secondary education, leading to a decrease in student population growth across the United States.

At the time, Ward Body Works was among "the Big Six" full-line school bus manufacturers (alongside Blue Bird, Carpenter, Superior, Thomas, and Wayne).

With company president Charles Ward selling off his stake in the company, Ward Industries was acquired by an investment group (assisted by then-Arkansas Governor Bill Clinton) named MBH, Inc. MBH was an acronym for the first letters of the last names of each of the 4 investors: Thomas E "Mack" McLarty, J.W.

As Ward Industries continued to hold significant market share in the school bus segment, AmTran chose to retain the Ward brand name for school buses although non-school bus products adopted the AmTran brand in 1981.

Using a shortened version of the Chevrolet/GMC B-Series, the Patriot allowed for a shorter wheelbase and nose angle for improved forward visibility.

In 1987, the structure of the Ward/AmTran body underwent an exterior update, distinguished by a rubrail mounted below the window line.

Much of the body structure remains in use in current-production IC Bus CE and RE-series product lines.

In 1991, Navistar International acquired one-third of the stock of American Transportation Corporation; the purchase was initiated by Jerry Williams, the CEO of AmTran at the time.

The first rear-engine bus produced by AmTran or Ward in over 20 years, the RE broke from industry precedent in not sharing a common body design with the front-engine Genesis.

To focus on full-size buses exclusively, AmTran ended production of the Vanguard cutaway-chassis bus after 1996.

The drivers' compartment was redesigned with updated controls and the flat windshield was replaced by a 4-piece design to improve forward visibility.

Though still headquartered in Conway, the factory was now rededicated towards the lower-volume AmTran FE and RE-series product lines.

Branded as a fully integrated conventional (pairing an International-sourced chassis, powertrain, and body), the IC underwent several design updates.