Data link is the exchange of information to or from the airplane using a radio connection to ground-based server.  

Data link traditionally is with reference to Aircraft Communication, Addressing and Reporting System (ACARS).  ACARS is a limited-character set store-and-forward messaging service that can operate over VHF, HF, and satellite networks.  IFE server applications may utilize an ARINC 619 ACARS end-system interface by way of an ARINC 429 connection to an ARINC 758 Communications Management Unit.  As aircraft architectures abandon ARINC 429 in favor of forms of Ethernet using an IP network, the connection to IFE for ACARS messaging may become difficult (network security concerns).  IFE may choose alternatively to utilize a Ku/Ka or ATG Internet access radio service provided for passenger entertainment as an alternative data link.

The following tables step through the steps necessary to deliver a message to the IFE using various networks.  A manual alternative to data link is pilot voice transcription, whereby the message is communicated to the pilot over a voice channel from the ground, and the pilot transcribes the message for either cabin attendant or IFE presentation.