The nuclear-powered attack submarine USS Illinois completed its alpha sea trails over the weekend, General Dynamics Electric Boat announced Monday.

It was the first voyage for SSN-786, the 13th Virginia-class boat, on the open seas, the company said in a statement.

Illinois' alpha sea trails were comprised of a variety of submarine and propulsion plant operations, submerging for the first time and high-speed runs on and below the surface in order to show the propulsion plant is mission capable.

Electric Boat and its construction partner, Newport News Shipbuilding, a subsidiary of Huntington Ingalls Industries, have already delivered 12 Virginia-class submarines to the U.S. Navy.

Fifteen more boats in the class are under contract.

Virginia-class submarines displace 7,835 tons, with a hull length of 377 feet and a 34-foot diameter.

They can hit speeds of more than 25 knots and can dive deeper than 800 feet.

They also sport Mark 48 advanced capability torpedoes and Tomahawk missiles.