The group, which also includes three Belarusians and two Russians, was formally charged on Monday, eight months after they were detained.
The 24 accused insist they were working as oil industry contractors.
One of the Russians has told the BBC that their release could already have been secured through diplomacy.
In a phone interview, Aleksandr Shadrov, 59, told the BBC Russian Service that they had all been in Libya purely to service oil rigging equipment and that a good lawyer would "easily refute the case".
They deny the charges of preparing land-to-air missile launchers to shoot down planes taking part in the Nato-led mission to protect Libyan civilians.
Mr Shadrov believed the problem was that Russian officials had probably waited for "some sort of overarching authority [in Libya]. What they needed to do was reach an agreement with the commanding officer of the group holding us under guard."
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