The 41st US president died Friday at age 94, at his home in Houston -- "a very gentle and peaceful passing," his lifelong friend and advisor James Baker said Sunday on ABC's "This Week."

Bush -- only the second president to see his son follow him to the Oval Office -- will be honored with four days of services and tributes in Washington and in Texas, where he will be buried on Thursday.

The high point of the commemorations will come Wednesday with a state funeral at Washington National Cathedral -- the first presidential funeral since Gerald Ford died in 2006.

Bush was a decorated World War II fighter pilot, former head of the Central Intelligence Agency, and vice president to Ronald Reagan before winning the White House.

President Donald Trump -- who has often clashed with the Bush family -- has declared Wednesday a national day of mourning, and said he will attend the funeral.

- Lying in state -

The week's events begin at 1630 GMT Monday, when Bush's remains are to be flown aboard the presidential Boeing 747 -- made available at Trump's direction -- from Houston to Joint Base Andrews, Maryland.

By tradition, the plane is only known as Air Force One when the sitting president is on board.

Family spokesman Jim McGrath said the flights to carry Bush are being dubbed "Special Air Mission 41."

"A beautiful day In Texas -- 'ceiling and visibility unlimited,' Mr. President," he wrote -- using a phrase that Bush held dear from his time in the Navy, and one used by his family and friends to discreetly spread the news of his death.

Bush's son George -- the 43rd president of the United States -- and other loved ones are expected to travel on the presidential jet.

Also reportedly expected to make the trip is his service dog Sully -- McGrath posted a touching photo of the yellow Labrador near Bush's casket on Sunday with the phrase "Mission Complete."

After a speech from Vice President Mike Pence, Bush will lie in state in the US Capitol from Monday evening until Wednesday morning, under the watchful gaze of an around-the-clock honor guard.

Thousands are expected to pay their respects.

The casket will then be transported to the cathedral for Wednesday's funeral service -- the fourth held there for a former president.

Dozens of foreign leaders and US luminaries are expected.

Former Canadian prime minister Brian Mulroney told Politico he will deliver one of several eulogies, at Bush's request.

The casket will then be flown back to Houston, where the former head of state will lie in repose at St Martin's Episcopal Church -- where the Bushes worshipped for decades -- until Thursday's funeral service.

The remains will then be transported by train for interment at the George Bush Presidential Library in College Station, Texas.

Bush will be buried next to his wife Barbara, who died in April, and their daughter Robin, who died of leukemia at age three.

- Tributes from friends -

Baker, who served Bush as secretary of state, joined others in paying warm tribute on Sunday television talk shows.

Baker called him "far and away the best one-term president we have ever had," alluding to Bush's single biggest political failure -- his loss in the 1992 election to Bill Clinton.

Baker instead emphasized his friend's foreign policy successes: navigating the end of the Cold War, negotiating two nuclear arms reduction treaties, and summoning a global coalition to eject Iraqi troops from Kuwait in the first Gulf War.

Colin Powell, who was chairman of the Joint Chiefs of Staff during that war, said he was confident in Bush's leadership because "he knew what combat was all about. He knew it meant the death of people... He wanted to avoid a war."

The former president had struggled for years with Parkinson's disease, which left him wheelchair-bound and often hospitalized -- including after Barbara's death.

Last week, things took a decided turn for the worse, Baker said on ABC.

When an aide told Bush that Baker was visiting Friday, "he perked up. He opened his eyes. He looked at me, he says, 'Hey, Bake. Where we going?'"

"We're going to heaven," Baker said.

Bush replied: "Good, that's where I want to go."

Baker said Bush's last words, in a phone conversation with son George, were: "I love you, too."