The pilot has been identified as Paul Reedy. Reedy, according to the national guard, died in the crash while his student, lieutenant Hisham bin Abdulaziz Al Al-Sheikh sustained injuries and has been admitted to hospital. Reports say Hisham is responding to treatment.
The pair was on board a Boeing AH-6i, a light attack and reconnaissance helicopter.
The National Guard did not say whether the American citizen was a soldier or not.
The US is one the kingdom’s leading arm and training supplier.
Ties between the two countries have been strengthened under President Donald Trump who chose the kingdom for his first foreign visit, May last year.
The US is also assisting the kingdom in Yemen alongside the United Arab Emirates (UAE) and several other countries, in their drive to shore up the authority of President Mansour Hadi who has been flashed out of the Yemeni capital, Sanaa, by Iran-backed Houthi rebels.