KIEV : Direct flights between Ukraine and Russia were grounded Sunday as mistrust between the uneasy ex-Soviet neighbours boiled over into a new trade war that affects tens of thousands of families.

"I never thought it would come to this," said 30-year-old Muscovite Alexander Mikhaylin after walking off the very last Russian flight into Kiev's sprawling Boryspil airport late Saturday night.

"Of course it will make life more difficult," the IT specialist said while wearily still clutching his red Russian passport after passing the customs zone. "These were the cheapest and most convenient tickets," he sighed.

Russia and Ukraine share both a long history and a fierce animosity sparked by months of winter 2013-2014 protests that ousted Kremlin-president Viktor Poroshenko and brought a strongly pro-Western leadership to power.

Ukraine's decision to escape Moscow's orbit set off a bloody chain of events that included Russia's March 2014 seizure of Crimea and the 18-month eastern separatist conflict that has killed at least 8,000 people.

Russian President Vladimir Putin denies choreographing the eastern revolt in reprisal for the change of heart in Ukraine - which Moscow saw as part of a new geopolitical bloc to rival the European Union and eventually NATO.

But Kiev and its Western allies refuse to believe him because Putin had also at first rejected suggestions that Russian forces had been dispatched to take over Crimea.

He later admitted on Russian state television that the entire operation had been well planned in advance.

The veteran Kremlin leader's tough approach to his western neighbour and seeming expansionist dreams launched a global trade war that saw Russia ban the import of most Western food.

Brussels and Washington's own sanctions that included foreign asset freezes of close Putin allies and partial bans on investments in Russia's vital energy industry.

The flight spat started with Poroshenko's September 16 announcement that Russian airlines would soon be barred from landing - but not flying over - Ukraine because of Moscow's refusal to hand back Crimea.

Russia denounced the decision as "madness" before taking similar measures this month.

A desperate round of negotiations between the two sides in Brussels on Friday ended without any immediate solution in sight.

Russian authorities estimate some 800,000 people flew between the two countries in the first eight months of the year.

They also say that at least 70 percent are Ukrainians trying to visit Russian relatives and that it was Kiev's main airline that was likely to be financially hurt the most by the air blockade.

Travellers must now look into other less convenient, more expensive options including slow overnight train rides and flights via other countries on relatively good terms with both sides.

Ukrainians could for instance first travel west to Moldova before making the longer flight back across their own country to Russia.

Other options include Belarus - its main airport in Minsk now standing largely empty because of the country's poor relations with the West - as well as ex-Soviet Georgia.

Travellers could also potentially use the three Baltic countries and their sleek new airports.

But the tiny ex-Soviet nations are proud members of European Union's Schengen free travel zone.

People without such a visa are required to stay cooped up - often for many hours - in the grim waiting areas because they cannot legally leave the airports.

Schengen visas require a painful registration and screening process that ends with denials in cases when people fail to prove they have no intention of staying in the European Union and have the financial means to fend for themselves.