The Queen has made her first public appearance of the year outside Windsor Castle, to mark the centenary of the Royal Australian Air Force.
The monarch said she was "delighted" to attend the service at the Commonwealth War Graves Commission Air Forces Memorial in Runnymede, Surrey.
The Queen was last seen in November, at the Cenotaph in London for Remembrance Sunday.
It has been two weeks since her husband, Prince Philip, left hospital.
The Duke of Edinburgh, 99, had been treated for a heart condition and returned to Windsor Castle on 16 March.
At the ceremony, which began with a flypast by the Red Arrows, the Queen paid tribute to the "skill and sacrifice" of the RAAF.
Sending her "best wishes and congratulations" to the RAAF, she wrote in a foreword to the order of service: "Throughout my reign, the Royal Australian Air Force has shown immense dedication to duty and has defended our freedom in many conflicts around the world."
More than 350,000 men and women have served in the RAAF since its formation in 1921. They have fought in conflicts ranging from the Second World War to Korea, Vietnam, Afghanistan and Iraq.
Wednesday's event was the fourth royal engagement the Queen had attended outside the walls of Windsor Castle since the pandemic began.
The Queen has taken part in a number of virtual royal engagements via video call during the pandemic, while a number of high-profile events have been staged in Windsor Castle's grounds.