At 2:56 p.m. Eastern European Summer Time (11:56 GMT), it departed from the Ukrainian capital. The jet is now flying over Slovakia.
The development comes as US cargo ship was reported to have docked in Ukraine's Odessa port in late March, carrying 350 tonnes of military equipment and vehicles for the country's armed forces.
Earlier in March, the US Department of Defence announced additional $125 million package for the Ukraine Security Assistance Initiative to cover training, equipment, and advisory support. The remaining $150 million appropriated by Congress will be provided to Ukraine in 2021 once Pentagon certifies the country's progress on key defense reforms.
In total, the US has committed over $2 billion in security assistance to Ukraine since 2014.