The Wordshop will handle global B2B comms, including analyst relations, on an account thought to be worth around £70,000 a year.
It is led by The Wordshop director Charlie Pryor, who reports to TriaGnoSys MD Axel Jahn.
The agency already handles PR for the OnAir system, a joint venture between Airbus and tech firm Sita Inc to provide inflight mobile services. It uses the TriaGnoSys software.
Air France is expected to adopt the technology for its passengers next February.
Pryor said: 'It will become the industry standard. Passengers will want it and airlines will have to provide it.'
Signals from passengers' phones travel to a small 'base station' on the plane, which then directs the signal to a satellite. Calls, emails and SMS messaging will be billed at roaming rates.
It will not, however, be possible to send emails from laptops on the new system. The technology can be used on trains and ships though.
The Wordshop will bid to build TriaGnoSys's reputation in the global satellite comms market by winning coverage in mobile, technology, air and maritime transport media.
Two rivals, ARINC and Telemor, have a joint venture product, called AeroMobile, which also allows passengers to use mobiles inflight.
They have both signed an agreement with Boeing – but not with an airline operator as yet – to fit the technology in its planes from the end of this year.