© Associated PressLost: The group had reportedly been drinking when they set off in an AN-2 biplane like this one at 11pm
Rescue teams have scoured the area but have been unable to find a trace of the AN-2 biplane, which set out without permission from a regional airport in Serov, near Yekaterinburg.
The families and friends of the missing group can only hope they have stranded somewhere without means of communication, in echoes of the popular TV series Lost.
Up to 2,000 people and 14 aircraft have been involved in the desperate hunt for the AN-2 biplane over 275,000 square kilometres of rough terrain, according to the Daily Telegraph.
Policeman Valery Gorelykh told reporters the group had set off on their unscheduled flight at 11pm, after a drinking session.
He said one theory was that they intended 'to go fishing or to a bathhouse' - steam saunas often found in remote parts of Russia.
The group included a pilot, Serov's chief traffic policeman, another officer, a security guard and the airfield's night watchman - who was reportedly wearing slippers - along with some of the men's relatives, including at least two women.
The rescue operation has been tricky because part of the region is hilly and covered in dense forest known as 'taiga'.
© ReutersNo trace: Firefighters and investigators examine wreckage near the Ural mountains after an airliner crashed there in 2008
Andrei Zalensky, head of the regional emergencies ministry, said it was possible the missing had not died.
'Even if some of them are injured they could survive, but they won't be able get out on their own. We must continue to search.'
Psychics intrigued by the new mystery have rushed to offer their help in locating the plane, but Mr Zalensky said their efforts were in vain.
He said: 'If I marked on a map every point suggested by a psychic and joined them up I would have a flower 500km across.'
Last week, the families of four of the missing people wrote to Vladimir Putin, Russia's president, asking him to step up the search effort.
The plane is owned by a local company, Avia Zov, and had been employed to fight forest fires
A mechanic working at the airfield from which it left said he saw the take-off and tried to stop the pilot, Khatim Kashapov.
The mystery surrounding its disappearance is reminiscent of the infamous Dyatlov Pass incident, in which nine ski hikers perished in odd circumstances in the northern Urals in 1959.
When their bodies were found, two victims had cracked skulls, two had broken ribs and one had her tongue missing, although there were no signs of struggle at the scene.
A Soviet investigation concluded the team died as the result of 'a compelling unknown force'.
I think it's the same incident that happened June 11, 2012? _[Link](Russian source)
Apparently several planes and people disappeared in this area of Ural mountains. One of them, was a plane piloted by Dyatlov's friend, Gennadiy Patrushev: _[Link] (Russian source) [quick translation]
"Only in the middle of February, a pilot Gennadiiy Patrushev discovered the first two bodies from the air, and called for a rescue team to the place of tragedy. [He] knew the members of the group very well, when they were still alive...
....
During a period of 1960-196, nine pilots and geologists altogether found their tragic deaths in this accursed place. One of the planes was by piloted by Patrushev. When Patrushev's plane was found, on the wreckage traces of with radiation were discovered."