The IBM 9020 was an IBM System/360 computer adapted into a multiprocessor system for use by the U.S. FAA for Air Traffic Control. Systems were installed in the FAA's 20 en route Air Route Traffic Control Centers (ARTCCs), beginning in the late 1960s. The U.K. CAA also installed a system in its London centre. The IBM 9020A, for example, was based on the S/360-50 and the 9020D used two out of three or four S/360-65 processors for flight and radar data processing with two out of three S/360-50 processors providing input/output capability. The Raytheon CDC could drive a maximum of 60 PVDs. The five ARTCCs that exceeded this requirement were equipped with the IBM DCC which could drive up to 90 PVDs.

The air traffic control software ran on a modified version of OS/360 MVT as an embedded operating system, OS/9020, also referred to as the “Monitor”. The monitor provided communications, storage management, timing, scheduling and recording services. That software was written in JOVIAL. JOVIAL is particularly well suited to managing tables and linked lists which are used extensively in the system. The support tools, assemblers and compilers also ran on OS/9020. was signed between the FAA and the Civil Aviation Organization of Iran. Under the terms of the treaty the FAA would provide technical assistance to improve the Iranian National Airspace System. This assistance included the installation of a 9020D and 9020E and associated equipment at a cost of $29m (out of a total contract cost of $272m). The treaty fell foul of the 1979 Iranian Islamic Revolution and the systems were never delivered.

{| class="wikitable"

|+ ARTCC System Configurations

|-

! ARTCC !! CCC !! Display

|-

| Albuquerque|| IBM 9020A || Raytheon 730

|-

| Atlanta|| IBM 9020D || Raytheon 730

|-

| Boston|| IBM 9020A || Raytheon 730

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| Chicago|| IBM 9020D || IBM 9020E

|-

| Cleveland|| IBM 9020D || IBM 9020E

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| Denver|| IBM 9020A|| Raytheon 730

|-

| Fort Worth|| IBM 9020D || IBM 9020E

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| Houston|| IBM 9020A || Raytheon 730

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| Indianapolis|| IBM 9020D || Raytheon 730

|-

| Jacksonville || IBM 9020D || Raytheon 730

|-

| Kansas City|| IBM 9020D || Raytheon 730

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| Los Angeles|| IBM 9020D || Raytheon 730

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| Memphis|| IBM 9020A || Raytheon 730

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| Miami|| IBM 9020A || Raytheon 730

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| Minneapolis|| IBM 9020A || Raytheon 730

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| New York City|| IBM 9020D || IBM 9020E

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| Oakland|| IBM 9020A || Raytheon 730

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| Salt Lake City|| IBM 9020A || Raytheon 730

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| Seattle|| IBM 9020A || Raytheon 730

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| Washington DC|| IBM 9020D || IBM 9020E

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| London (United Kingdom)|| IBM 9020D || Plessey PRDS

|}

Longevity and follow-on systems

The 9020As and 9020Ds were in service in North America until 1989 when they were finally replaced by IBM 3083 BX1 mainframes as part of the FAA's HOST Computer System (HCS) upgrade. The 3083s in turn were replaced with IBM 9672 RA4 parallel processing servers during the FAA's Host and Oceanic Computer System Replacement (HOCSR) completed in 1999. One reason for the 1999 upgrade was concern, probably unfounded, that the IBM 3083's microcode would not operate properly in the year 2000.