Transaero and UTair have applied for rights to serve London from St Petersburg.
The Russian airlines have submitted requests to Rosaviatsia for permits to operate scheduled flights between the two cities.
Last month, the Russian regulator and the UK's Civil Aviation Authority reached an agreement to add a second pair of designated carriers on the route, to join British Airways and Aeroflot subsidiary Rossiya.
BA carries out seven flights per week from London Heathrow airport to St Petersburg, but Rossiya has not exercised its flying rights yet.
UTair says it sees potential customer demand for services as there is still only one operator in the market.
Transaero plans to provide up to seven frequencies to London from St Petersburg, with the catchment area comprising northeastern Russia.
EasyJet, which started flying to Moscow from London Gatwick airport last year, is also likely to be awarded route rights to St Petersburg.