0928 GMT February 24, 2020
The flight was conducted under the Open Skies treaty on Thursday by a US Air Force OC-135 observation aircraft, the Pentagon said in a statement issued on Thursday.
Pentagon spokesman Eric Pahon told CNN that the “timing of this flight is intended to reaffirm US commitment to Ukraine and other partner nations.”
"Russia's unprovoked attack on Ukrainian naval vessels in the Black Sea near the Kerch Strait is a dangerous escalation in a pattern of increasingly provocative and threatening activity," he added.
"The United States seeks a better relationship with Russia, but this cannot happen while its unlawful and destabilizing actions continue in Ukraine and elsewhere,” according to the Pentagon statement, Presstv Reported.
The Pentagon spokesman said the last such "extraordinary" observation flight over Ukraine happened in 2014 after the Russian military intervened in Crimea.
The Pentagon statement said American, Canadian, German, French, United Kingdom, Romanian and Ukrainian observers were on board the aircraft during the observation flight.
Meanwhile, the United States has also sent a guided-missile destroyer near the contested waters of the Sea of Japan, off the Russian coast.
The US Navy USS McCampbell on Wednesday sailed in the vicinity of Peter the Great Bay, near the Russian Pacific Fleet base in Vladivostok, in a first such stunt since 1987 — the peak of Cold War tensions with the former Soviet Union.
The US navy is also preparing to send another warship into the Black Sea in the near future, a move that could worsen the tensions even further.
Tensions over Ukraine escalated on November 25, when Russian border patrols fired at three Ukrainian ships and then seized them along with their sailors because of illegal entry into Russian waters in the Kerch Strait, which connects the Black Sea and the Sea of Azov.
The incident took place near Crimea, a former Ukrainian territory on the Black Sea that joined Russia in a referendum in March 2014.
The seizure of the Ukrainian ships sparked a fresh row between Moscow and Washington and prompted US President Donald Trump to cancel a planned meeting with his Russian counterpart, Vladimir Putin, on the sidelines of the G20 summit in Argentina.