The woman, identified as Victoria Kong, wandered off from the airport Friday evening and was seen strolling along the Mount Vernon trail, The Washington Post reported.
The trail, which is used by pedestrians and bicyclists, runs between the Potomac River and the George Washington Memorial Parkway, authorities said.
Searches for Kong continued Sunday. She was described 5 feet, 3 inches tall, 130 pounds and wearing a long purple/brown dress with a tan sweater jacket and sandals.
Family said Kong has shown early signs of dementia.
The Metropolitan Washington Airports Authority police asked anyone with information to call 703-417-2400.