The departing 45th US President addressed several hundred supporters from Joint Base Andrews, Maryland. He told the crowd: “Goodbye. We love you. We will be back in some form.”
Mr Trump received a 21-gun salute before boarding Air Force One for the final time.
Joe Biden was sworn in as the 46th US President late in the morning and Mr Trump refused to attend the inauguration, breaking presidential tradition.
Three former presidents – Barack Obama, George W Bush and Bill Clinton – were at Mr Biden’s historic event where Lady Gaga performed the National Anthem.
Departing Vice President Mike Pence passed the metaphorical baton to his successor Kamala Harris by waving her and others in the Biden team off from the Capitol’s steps.
But Mr Trump ended his term in power with less attention, according to Newsweek.
The publication notes the absence of Mr Pence and lists three White House staffers as present.
These are Mr Trump’s White House chief of staff Mark Meadows, senior adviser Stephen Miller and Acting US Secretary of Defense Kash Patel.
Ivanka Trump, Jared Kushner, Donald Trump Jr, Kimberly Guilfoyle and Tiffany Trump were also in attendance, alongside Mr Trump’s grandchildren.
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Speaking after taking the oath of office from Chief Justice John Roberts, President Biden said: “Democracy has prevailed.”
He also described the day as one of “history and hope”, adding: “My whole soul is in putting America back together again.”
Mr Biden urged Americans to “start afresh”. He said: “Let’s begin to listen to one another.
“We can see each other, not as adversaries, but as neighbours.”