The jets were responding to a float plane that had entered restricted presidential air space over Western Washington while President Barack Obama was in town.
The plane landed safely at a float plane harbor in Kenmore on the northern shores of Lake Washington.
Several calls from worried residents across the region, from Olympia to Edmonds, flooded emergency dispatchers and the KOMO newsroom reporting two distinct explosions that rattled windows and shook homes around 1:50 p.m.
A spokesman with the Oregon Air National Guard said two F-15s from their 142nd Fighter Wing were scrambled from their base at Portland International Airport.
NORAD spokesman John Cornelio said the float plane left the restricted area before the Air National Guard jets arrived, and there was no intercept. A source told ABC News the plane landed just before the fighter jets got to him.
The Cessna 180 float plane was flying to a seaplane base on Lake Washington, next to Seattle, from Lake Chelan in Eastern Washington, said passenger Laura Joseph, of Normandy Park. She told The Associated Press that neither she nor the pilot, Lee Daily, knew about Obama's visit or the air restrictions that accompany such a high-profile trip.
Joseph said she saw an F-15 outside the window as the plane approached Seattle.
"I saw a jet, just a white jet going by," she said. "I thought it was kind of odd to see a military jet."
The fighter only passed by the float plane once and didn't take any other action, Joseph said.
"The jet didn't come by us or anything. Just flew by, and it didn't circle us or do anything," she said.
Joseph said she and Daily didn't know anything was wrong until they landed and were told they had to talk to the Secret Service. She also said she didn't hear the sonic booms.
"(We) taxied in and parked the plane. The guy came out and said, 'You guys weren't supposed to be up; it's a no-fly zone,'" she said. "(I thought,) 'Are we in trouble? Are we going to jail?' That's all. I was just scared, mostly for him (Daily)."
Joseph said she and Daily were allowed to leave after being interviewed by the Secret Service and haven't heard anything yet about possible sanctions.
"Oh my God, I can't believe - is this the top news thing?" she said.
Joseph said Daily is a seasoned pilot who just had "a mishap, just a mistake."
"He's had that plane for 25 years. He's a pretty seasoned pilot ... We just didn't know," she said. "He's so careful and cautious, and I totally trust him."
Pierce County Det. Ed Troyer said the incident took down 911 service across parts of Pierce County for about an hour as dispatch centers were flooded with calls, but service was restored just before 3 p.m.
"Many house and car alarms have been set off that we will not be able to respond to," he said.
In a statement Tuesday evening, the Oregon Air National Guard said the jets were cleared to accelerate to supersonic speed minutes after takeoff. The Guard said the booms were heard by people from Longview, Wash., to the Puget Sound area.
Obama was in Seattle to stump for Sen. Patty Murray on a three-day campaign swing for endangered Democrats. Air Force One was on the ground at King County International Airport/Boeing Field in south Seattle at the time of the incident shortly after 1:30 p.m. The president's plane departed Seattle at 3:47 p.m.
Oregon Air National Guard Staff Sgt. John Hughel said the F-15s were scrambled by NORAD from Portland International Airport. He said the guard has two fighters always on alert to patrol the air space from central California to the Canadian border.
Watch the news conference with Portland National Guard: