Nazanin Zaghari-Ratcliffe was detained in Iran for nearly six years after being arrested while taking her daughter to see her family.
She was accused of plotting to overthrow the Iranian government, which she denied.
Labour's Tulip Siddiq, the family's local MP, tweeted an image of Mrs Zaghari-Ratcliffe this afternoon, wearing a yellow top and a grey scarf, smiling on the window seat of a plane.
