The shooting-down of a Syrian jet by the United States is believed to be the first air-to-air kill by a manned US aircraft since 1999.
Despite Hollywood blockbusters showcasing aerial dogfights, they have almost vanished from modern warfare.
In the 20th Century, skilled pilots who clocked up kills were often referred to as aces.
The US considers a pilot with at least five confirmed kills to be an ace - but no serving pilot holds the title.
What was the lesson of the Gulf wars?
A report published by the Center for Strategic and Budgetary Assessments (CSBA) in 2015 found just 59 kills since the 1990s - the large majority of which were in the First Gulf War.
Later that year, when Turkey shot down a Russian Su-24 plane along the Syrian border in a rare conflict, it sparked an international diplomatic row