Britain's Queen Elizabeth II and her husband, Prince Philip, have traveled by vintage carriage for the "Trooping the Colour" parade. Singer Rod Stewart is among those to be knighted to mark the occasion.
Thousands of people thronged the streets of the British capital for Saturday's colorful military ceremony, between the Queen's London residence, Buckingham Palace, and Horse Guards Parade ground, nearby.
The parade and colorful military ceremony featured more than 1,500 soldiers and officers and several hundred horses.
Several other royals, including the Duchess of Cornwall and Prince Harry, also rode in carriages along the city's famous Mall, a road which leads to the palace.
Part of a weekend of commemorations to mark her 90th birthday, the monarch was greeted with a royal salute, before carrying out an inspection of the troops.
Dating back to the 18th century, the "Trooping the Colour" event takes its name from a ceremony to hand over the Colour, a regimental flag, and parade it through ranks of troops.
Pomp and pageantry
Later, the royal couple was expected to make an appearance on the balcony of the palace, to wave to the crowd as Royal Air Force jets and some vintage World War II planes fly overhead.
One-year-old Princess Charlotte was widely expected to make her first balcony appearance with her parents, Prince William and his wife Kate.
Also on Saturday, British singer Rod Stewart was knighted in the Queen's birthday honors, an annual award of decoration and medals. The title means the musician responsible for the hits "Do ya think I'm sexy" and "Maggie May" will now be referred to as Sir Roderick David Stewart.
"Downton Abbey" star Penelope Wilton was made a dame, the female equivalent of a knight.
British astronaut Tim Peake, who is currently in residence on the International Space Station, and war-era singer Vera Lynn also received royal honors.
The festivities continue Sunday with a massive street party in front of the palace. Around 10,000 people who work at charities supported by the Queen have been invited to the open air festivities.
Street parties will also be held in many towns and cities throughout Britain and in other Commonwealth countries.
The Queen's real birthday is in April. The official birthday is timed in hope of fair weather - a custom that began in the 18th century.
Born in 1926, the Queen has ruled since 1952, when she was 25 years old. In September, she surpassed the six-decade reign of Queen Victoria, her great-great grandmother, who sat on the throne from 1837 to 1901.
mm/rc (AP, dpa, Reuters)