"Before passengers can use their mobile telephone on board an aircraft, there must be an acceptable agreed legal basis to do so," OnAir said in a news release on Tuesday.
"OnAir now expects the compatibility study for Europe to be finalised around February 2006."
OnAir has estimated a potential market of more than 700 million users by 2009 for the technology, which would allow passengers to use mobiles, laptops and PDAs on planes and pay through their own phone company or Internet service provider.
It has proposed that the national telecoms regulator where a plane is registered be in charge of licensing its onboard mobile phone system.
The firm wants a framework agreement to ensure that only one licence will be required for planes flying across Europe and has been working within the Conference Europeenne des Postes et Telecommunications (CEPT) on this. The Electronic Communications Committee (ECC) co-ordinates CEPT's telecoms activities.
"The ECC has decided to include several technical parameters into the framework," OnAir said in explaining the time still required to finalise the agreement.
Airbus, Swiss-based SITA Inc and US firm Tenzing Communications Inc announced plans to form OnAir in July.
The system it is working on would route mobile phone calls via a small onboard base station, or "picocell", and use the Inmarsat satellite communications network to reach terrestrial telephone networks.
Test results announced in September showed the system did not interfere with aviation electronics.