Normally the White House lowers them on the day of death and the day after, which would be Saturday and Sunday, which they did, then they raised it. This extends it through to the day of burial.

Via Fox News:

President Trump announced Monday he ordered the American flag to fly at half-staff through this coming Sunday to honor the late Sen. John McCain.

“Despite our differences on policy and politics, I respect Senator John McCain’s service to our country and, in his honor, have signed a proclamation to fly the flag of the United States at half-staff until the day of his interment,” said Trump, who added that Vice President Mike Pence would make remarks at Friday’s ceremony honoring McCain at the U.S. Capitol.

McCain will lie in state at the Capitol for the remainder of Friday. A memorial service will be held at the National Cathedral in Washington the following day before McCain is laid to rest at the U.S. Naval Academy Cemetery in Annapolis, Md., on Sunday.