Here's why flags are flying at half-staff, and why President-elect Donald Trump isn't thrilled with the decision.

President-elect Donald Trump railed against the order for American flags to be flown at half-staff to honor the late President Jimmy Carter, complaining that they will be in that position “for the first time ever during an Inauguration of a future President.

Carter, the 39th U.S. president, died on Sunday at 100 years old. President Joe Biden ordered that the flags of the United States be flown at half-staff at the White House and public buildings and grounds for a period of 30 days following Carter’s death in honor of him.