The president of the US, Barack Obama, has lifted the arms embargo placed on Vietnam since 1984, describing it as "lingering vestige of the Cold War". Vietnam is involved with other countries in several maritime disputes with China. As a consequence, it has increased it's defence spending.
Vietnamese Su-22 (Copyright in the photo).
Vietnamese Armed Forces are mostly equipped with Soviet/Russian hardware. The decision will allow acquisitions of US equipment. This would allow Vietnam to diversify suppliers. The Air Force could be interested in refurbished F-16 to replace the Su-22/MiG-21 fleet. Maritime patrol aircraft could be of special interest as Vietnam will need to reinforce these capabilities when facing China.
References: