Russian President Putin has called in some of his country's reserve troops.
After his address, tickets for Istanbul and other destinations sold out.
A 30-year-old Russian who lives in the UK said his friends are desperate to leave.
The tickets for flights out of Russia sold out after Putin's announcement.
The next phase of Putin's invasion of Ukraine was announced in a rare address to the nation.
Prices for plane tickets out of Moscow sold out after the announcement.
There are flights to countries that allow Russians to enter without a visa.
There are no flights to Istanbul from Moscow for the next three days.
Aeroflot flights from Moscow are sold out until the weekend.
The airline did not reply immediately.
According to Aviasales, tickets for flights departing to Istanbul, Yerevan, and Belgrade, Serbia, on Wednesday are no longer available.
Russia's most popular website for buying flights is Avia sales. There was a spike in searches after the announcement.
As a ranked officer in reserve, my brother-in-law would have been first to be used in Putin's meat grinder.
I think it's too late for other people to scramble for tickets as he has already left to Turkey.
Russian Defense Minister Sergei Shoigu said 300,000 Russians would be called up to fight.
Shoigu said that only Russians with military experience will be called up.
According to The Guardian, a decree signed by Putin on Wednesday stated that the contracts of soldiers already fighting in Ukraine would be extended.
A 30-year-old Russian who lives in the UK is talking to his friends in Russia to find out if they can leave the country.
I'm ashamed of my country and it's hard to imagine how this can affect people there. I don't like war.
It is not known how many Russians have left the country since the beginning of the invasion.
After the invasion, the EU banned air travel from the country, but many Russians can still get into the EU by land.
Four of the five EU countries that border Russia have begun turning Russians away as a result of the sanctions.
Business Insider has an article on it.