Boeing has started assembly in Renton of the first P-8A Poseidon for the Navy, an anti-submarine plane that will replace older propeller-driven P-3 Orions.

The new jet uses the body of a 737 commercial jet, modified to deploy buoys to track subs and with a door in the bottom to launch torpedoes. It can also carry guided bombs and anti-ship missiles.

Also called the Multi-mission Maritime Aircraft, or MMA, the plane will be packed with high-technology tracking and communications equipment.

The first flight is scheduled for next year.

The Navy plans to purchase 108 of the Poseidons and put the first squadron into operation in 2013.