298 people aboard the flight were killed when the passenger jet was shot down over eastern Ukraine. According to a passenger manifest provided by Malaysia Airlines, nine Britons were among the dead.
Prince William addressed reporters outside Australia House in London on Friday.
"I know that I speak for all us here when I acknowledge our deep sadness following yesterday's disaster in Ukraine. ... For all of us who've lost fellow countrymen and women in the tragedy, words cannot do justice to our sense of loss.
"... For Australians and for our Malaysian brothers and sisters in the Commonwealth, the crash is a particularly cruel tragedy, coming so soon after the loss of MH370.
"... Please be assured of my family's thoughts and prayers at this time."
An investigation is underway to determine which party was responsible for firing a surface-to-air missile at the passenger jet. British Prime Minister David Cameron said Friday that "those responsible must be held to account and we must lose no time in doing that."
U.S. President Barack Obama also commented on the attack Friday, acknowledging that while the investigation is on-going, "we're beginning to draw some conclusions," and those conclusions point toward Russian-provided equipment and training to separatists in eastern Ukraine.