What was that military plane doing making lazy circles over Seattle?

There have been a lot of planes flying over Seattle recently, but one plane has drawn extra attention.

It’s a surveillance aircraft that Tyler Rogoway with The Warzone (Time. Inc) describes as “highly-modified for the special operations surveillance role.”

It is covered in a dizzying array of blisters, protrusions, humps and bumps. These include missile approach warning detectors and large fairings on its empennage for buckets of forward-firing decoy flares…

You can see an close-up photo of the plane here.

The plane, which goes by the call sign “SPUD21,” according to Rogoway, was flying over the Greater Seattle area and Portland for more than a week. It’s last flight recorded on flightaware.com departed and arrived at Boeing Field. The plane circled Seattle numerous times before landing — similar patterns are seen for most trips.

Rogoway told Seattle’s Morning News that the plane could have the capability of wide-area aerial surveillance. The kind of technology used to track enemies overseas for days on end.

Though Rogoway had trouble getting any kind of official statement about the plane, he was eventually told it was part of special operations command training. That’s about all anyone would tell him, however.

It’s unlikely the plane is meant to track anything nefarious in the area. Rogoway says the plane’s crew could be taking advantage of the Puget Sound region’s unique geography to train.

“Seattle is a great place to test this,” he said.

Listen to the entire interview here.