The ATC industry is moving from AFTN to AMHS as the industry standard approach to supporting ground to ground messaging. The initial AMHS rollouts have been centered on international connectivity, and the provision of AMHS/AFTN gateways in order to connect existing services to the new AMHS Infrastructure.

The second stage of the AMHS roll-out will deliver AMHS directly to the end user. A common method of providing ground to ground messaging services is by use of an AFTN Terminal. As the infrastructure moves to AMHS, these will be replaced by AMHS Terminals, a trend that opens up new opportunities for vendors who provide ground to ground messaging applications and interfaces.

What is an AMHS Terminal?

Those users who require access to messaging services and the associate applications such as flight planning, need a system which provides these services only (and not a general purpose ATM system). These users, usually low and medium volume users, currently make use of AFTN Terminals for which AMHS Terminals would be a direct replacement.

The AMHS Terminal interface to the end user would be very similar to that provided by an AFTN Terminal. The underlying AFTN communication would be replaced by AMHS to give direct delivery of the ATS Message Service. There are two components to this.

  • Access to AMHS for submission and delivery of messages uses X.400 P7 to access M-Store X.400. The Message Store will provide a managed system for storage and backup of messages, including meeting ICAO 30 Day archiving requirements.
  • The ATN Directory, for verification, capability, security and address mapping information. The address mapping is particularly important, as it will enable the user to be presented with familiar AFTN addresses, which Isode's API can convert to AMHS addresses using the ATN Directory.

You can see some exmaples of AMHS Terminals produced by Isode's partners here.

Benefits of AMHS Terminals

Given that the core ATC applications remain the same regardless of the ground to ground messaging standard, many of the benefits of AMHS Terminals over their AFTN predecessors relate to management and quality of service.

Benefits are discussed in more detail in the Isode white paper"Delivering the ATS Message Service to the End User using AMHS" but briefly include:

  • Improved robustness, due to use of ATN directory for address and capability validation.
  • Removal of restrictions on message size.
  • Improved security, with digital signature validation.
  • Archiving ability, meeting ICAO archive requirements.

In addition, structurally AMHS offers greater capabilities than AFTN and when the AMHS infrastructure is widespread, it will be practical to deploy new applications over that infrastructure. For example, the new BUFR system (Meteorological data) can take advantage of AMHS delivery.

Whilst AFTN terminals require special communication hardware, an AMHS terminal can use standard communication networks (e.g., an Internet connection), meaning that an AMHS terminal is essentially a software solution. This removes the support burden associated with managing special purpose hardware and can deliver cost benefits as standard hardware can be shared with other applications.

Isode enables AMHS Terminals

Isode provides AMHS infrastructure but not ATC applications, we do not and will not supply AMHS terminals. We supply APIs which provide the client side protocol support to integrate applications with AMHS, including ATN Directory.

These APIs have been designed to be simple to use, and in particular are suitable for support of an AMHS Terminal. They are also designed to assist the conversion of AFTN Terminal into an AMHS Terminal. In particular:

  • The AMHS Client API provides support for sending and receiving messages through a P7 Message Store.
  • The ATN Directory Client API, as well as giving general purpose directory access, provides a mechanism to convert between AFTN addresses and AMHS addresses. This will mean that an initial implementation does not need to make GUI changes, and end users can continue to work with AFTN addresses, which are mapped by the underlying infrastructure.


There is a clear market trend towards AMHS and, by implication AMHS terminals. Isode provides an easy and low cost way for AFTN Terminal vendors to address this new market in a cost competitive way.