The contract was apparently sealed after a Wednesday meeting between US Secretary of Defense Jim Mattis and Qatari Minister of State for Defense Affairs Khalid al-Attiyah, Reuters reported citing a source.
According to Bloomberg News, Qatar bought 36 warplanes produced by McDonnell Douglas, a subsidiary of Boeing.
The US approved the possible sale of up to 72 F-15QA aircraft to Qatar for $21.1 billion in November.
News of the deal comes less than a week after US President Donald Trump lashed out at the Gulf kingdom, saying it has “historically been a funder of terrorism at a very high level.”
Trump’s criticism emerged amid a diplomatic row between Qatar and other Arab nations, which demand that Doha stopped supporting the pan-Arabic movement Muslim Brotherhood and severed ties with Iran.
Qatar is a key American ally in the Middle East and an important exporter of natural gas. It also hosts the largest US military base in the region.