Police are searching for a woman last seen at Adelaide Airport last month.

Missing 20-year-old Rachael Moritz was reported missing on December 30 and South Australia Police believe she may be interstate.

She was last seen at Adelaide Airport on the morning of December 23, according to an unconfirmed tip off to police. She was in the company of a middle-aged woman, but detectives have no information to suggest that Ms Moritz is being held against her will.

Police are urging the Crime Stoppers caller who provided this information, and the woman who was with Ms Moritz at the airport, to contact police.Anyone who has any information is asked to contact Crime Stoppers on 1800 333 000 or online at www.sa.crimestoppers.com.au.