The Cessna 182 went down while attempting to land at Camano Island Air Park around 11:30 a.m., said Allen Kenitzer with the FAA.
The man on board was taken by ambulance to a local hospital while the woman had to be airlifted to Harborview Medical Center in Seattle, said Levon Yengoyan, assistant chief of the Camano Island Fire Department.
Yengoyan didn't give the extent of the injuries but said both patients were stable.
Dave Withstanley saw the crash happen and told KOMO News it was a classic stall situation where the plane didn't have enough air speed to maintain flight. He said the pilot gave the plane more power and nearly pulled out of the nosedive but slammed into the ground.
"He hit the ground level but really hard and then it tumbled over and broke the tail off; broke the engine off," Withstandley said.
He and about four or five others at the field ran to the wreckage and pulled the couple from the plane.
One of those running to the rescue was Steve Knopp, who owns the air field. Knopp said both inside were conscious but he had to keep talking to the man to keep him from blacking out. The woman complained of broken ribs and difficulty breathing.
The NTSB will investigate the crash.