She is understood to communicate with sign language and had been attending a deaf event at the bar.
Ms Aitchison is 5ft, slim, with long, dark hair. She was wearing a black top, cream skirt and black sandals.
She is understood to have been involved in an argument in the pub and is thought to have last been seen getting into a taxi.
Insp Leigh McManus, of Police Scotland, said: “Kirsty hasn’t been missing before and it is completely out of character for her not to keep in contact with her family and friends. She was reported missing to police on Sunday afternoon.
“Officers are carrying out extensive inquiries to trace her, and I would ask anyone with any information on her whereabouts to contact Shettleston Police Office through the non-emergency number 101.”