"He was a warrior, he was also a peace maker, and of course he fought and suffered during the Vietnam war, but then later as a senator he was one of the leaders who helped bring our countries back together, and helped the United States and Vietnam normalize our relationship and now become partners and friends", stated Daniel Kritenbrink, U.S. Ambassador to Vietnam.
The Arizona Republican died on Saturday of brain cancer.
Per Senate Minority Leader Chuck Schumer's (D-NY) communications director, Senate leadership is stepping in to get the flags lowered. His death had sparked an outpouring of tributes from across the political spectrum, except at 1600 Pennsylvania Avenue, where President Donald Trump has yet to utter a word about McCain since his passing.
In addition to raising the flag back to full staff, others noted that Trump never issued a proclamation noting McCain's passing. But presidents have the power to issue proclamations extending that period.
The White House did not immediately respond to a request for comment.
During Trump's 2016 presidential campaign - and after McCain's cancer diagnosis, which would prove to be fatal - Trump blasted McCain for being a prisoner during the Vietnam War.
During his involvement with a select committee on POW/MIA affairs, Mr McCain pressed for normalisation of diplomatic relations with Vietnam, something unpopular in the Republican party. "Our hearts and prayers are with you!"
More than 30 people have been honored by lying in state in the Capitol Rotunda, and only two individuals have lied in the Arizona State Capitol Museum Rotunda: Arizona State Senator Marilyn Jarrett in 2006 and Olympic gold medalist Jesse Owens, a Tucson resident, in 1980, according to McCain's office.
President George W. Bush was the first to make common practice lowering the staff for natural disasters, and President Barack Obama lowered the flag more than any other President.
McCain was a frequent critic of President Donald Trump on everything from his leadership style to his Russian Federation policy.
The McCain family had reportedly asked the president not to attend McCain's funeral even before he died this weekend at age 81. McCain will be buried at the U.S. Naval Academy in Annapolis, Maryland, on Sunday.