Saudi Arabia's Crown Prince Mohammed bin Salman attends a graduation ceremony for the 95th batch of cadets from the King Faisal Air Academy in Riyadh, Saudi Arabia December 23, 2018. Picture taken December 23, 2018. Bandar Algaloud/Courtesy of Saudi Royal Court/Handout via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY.

Graduate students take part in the graduation ceremony for the 95th batch of cadets from the King Faisal Air Academy in Riyadh, Saudi Arabia December 23, 2018. Picture taken December 23, 2018. Bandar Algaloud/Courtesy of Saudi Royal Court/Handout via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY.

Saudi Arabia's Crown Prince Mohammed bin Salman attends a graduation ceremony for the 95th batch of cadets from the King Faisal Air Academy in Riyadh, Saudi Arabia December 23, 2018. Picture taken December 23, 2018. Bandar Algaloud/Courtesy of Saudi Royal Court/Handout via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY.

Saudi Arabia's Crown Prince Mohammed bin Salman receives a gift during a graduation ceremony for the 95th batch of cadets from the King Faisal Air Academy in Riyadh, Saudi Arabia December 23, 2018. Picture taken December 23, 2018. Bandar Algaloud/Courtesy of Saudi Royal Court/Handout via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. Image for illustrative purposes.

Saudi Arabia's Crown Prince Mohammed bin Salman attends a graduation ceremony for the 95th batch of cadets from the King Faisal Air Academy in Riyadh, Saudi Arabia December 23, 2018. Picture taken December 23, 2018. Bandar Algaloud/Courtesy of Saudi Royal Court/Handout via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY.

Saudi Arabia's Crown Prince Mohammed bin Salman poses for photos with graduate students during a graduation ceremony for the 95th batch of cadets from the King Faisal Air Academy in Riyadh, Saudi Arabia December 23, 2018. Picture taken December 23, 2018. Bandar Algaloud/Courtesy of Saudi Royal Court/Handout via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY.

Saudi Arabia's Crown Prince Mohammed bin Salman attends a graduation ceremony for the 95th batch of cadets from the King Faisal Air Academy in Riyadh, Saudi Arabia December 23, 2018. Picture taken December 23, 2018. Bandar Algaloud/Courtesy of Saudi Royal Court/Handout via REUTERS

Graduate students take part in the graduation ceremony for the 95th batch of cadets from the King Faisal Air Academy in Riyadh, Saudi Arabia December 23, 2018. Picture taken December 23, 2018. Bandar Algaloud/Courtesy of Saudi Royal Court/Handout via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY.

Graduate students take part in the graduation ceremony for the 95th batch of cadets from the King Faisal Air Academy in Riyadh, Saudi Arabia December 23, 2018. Picture taken December 23, 2018. Bandar Algaloud/Courtesy of Saudi Royal Court/Handout via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY.

Saudi Arabia's Crown Prince Mohammed bin Salman attends a graduation ceremony for the 95th batch of cadets from the King Faisal Air Academy in Riyadh, Saudi Arabia December 23, 2018. Picture taken December 23, 2018. Bandar Algaloud/Courtesy of Saudi Royal Court/Handout via REUTERS ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY.