Russia says its participation in the Farnborough Airshow, beginning July 14 in Britain, is limited by visa problems.
The Russian Embassy in London wrote to the British Foreign Office that the visa difficulties affected "the arrival of the main part of the Russian delegation."
The Russian Embassy said in the letter demanding an official explanation that "technical workers in charge of the safe operation of exhibits Russia delivered" experienced particular difficulties.
Russian media have reported that 167 of the 347-member Russian delegation received visas.
Russian Deputy Minister of Industry and Trade Yury Slyusar said July 14 Russia would fulfill its scheduled meetings at the airshow "as quickly as possible due to limitations, and the Russian delegation will come back as quickly as possible."
There is no immediate British response.