ARINC Specification 620 defines the aircraft interfaces to the ACARS ground system operated by a Datalink Service Provider (DSP). It also defines the interface between the DSP and other ground-based datalink services. The datalink ground system standard definition supports traditional ACARS protocols as well as Media Independent Aircraft Messaging (MIAM) as defined by ARINC Specification 841. MIAM messages can be much larger than ACARS messages (5 MB versus 3.3 kB per message).
Supplement 9 includes methods to optimize the routing of MIAM messages. It adds ACARS Labels and Identifiers in support of Onboard Network System (ONS), Runway State Assessment, Aircraft Tracking for AOC Position Reporting, ATS Wind Services and Fight-deck based Interval Management System (FIMS) applications. It provides Media Advisory Codes for Broadband Systems (i.e., AeroMACS, Inmarsat SwiftBroadband (SBB) Satcom, and Iridium NEXT/Certus Satcom).