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Airlines For America (A4A)
From SKYbrary Wiki
Airlines For America (A4A) is a trade association formerly called the Air Transport Association (ATA) which represents the interests of the principal USA aircraft operators. It is perhaps best known worldwide for the ATA Classification, which is a technical numbering system used for aircraft systems by engineering and maintenance organisations, for sponsorship of the Maintenance Steering Group-3 (MSG-3) process and for the purposes of Minimum Equipment List (MEL) and Configuration Deviation List format.
For further information on A4A, see their website