The UK communications regulator has written to both firms urging them to take immediate steps to comply with conditions that came along with their spectrum holdings.
Inmarsat and Solaris were selected by the European Commission (EC) to operate mobile satellite services across Europe back in 2009.
Using spectrum bands 1980 MHz to 2010 MHz and 2170 MHz to 2200 MHz, both companies were to provide services such as broadcast, mobile and radio using satellite technology across Europe.
In the UK, Ofcom said it gave Inmarsat and Solaris authorisation to deliver such services using the allocated spectrum bands until 2027.
However, it said, a condition of this was that both companies were to be providing these services by 14 May 2011.
To date, Ofcom claimed in a statement, neither Inmarsat nor Solaris had taken the necessary steps to meet their commitments under the assigned frequencies.
Read more about satellite services
- Tour de France organiser ASO selects Globalstar satellite phones to keep support and emergency crews connected during UK leg of tour
- Ofcom launches a consultation into using higher frequency bands for satellite broadband connections, enabling faster speed for trains, aeroplanes and ships
As a result of this, Ofcom has now notified both companies that it has set a deadline of 1 December 2016 to bring the vacant spectrum into use.
If they do not, said the notices, Ofcom will “consider taking further regulatory action, in conjunction with other EC member states”.
“This could include a fine and/or revocation of that company’s authorisation in the UK,” said the regulator.
Inmarsat had already said it planned to use its spectrum to establish a hybrid network consisting of satellites and modified ground-based mobile network towers to provide connectivity to airline passengers passing over Europe.
In summer 2014 it revealed it was in advanced discussions with British Airways to launch the service.
Inmarsat did not provide further comment on the regulator’s ultimatum.