The Su-24 Fence appeared as a counter to the US swing-wing F-111 but unlike the latter has been continually modified to remain in the current Russian air arsenal. It is crewed by two in tandem, has 2x 25,000 lb st Lyulka AL-21F-A engines, 4-position swing wings from 16o-69o sweep, is armed with 1x 23mm GSh-6-23 cannon and can carry 9 tons of ordnance on 8 hard points and centerline. It is unique in that it can carry almost ALL Russian missiles and bombs up to nuclear. It can carry cluster munitions, dumb bombs, tv and laser guided bombs, various rocket launchers, AS missiles, AR missiles, and suppression weapons. On April 16, 2014 two Fencers baited the USS Donald Cook in the Black Sea. One loitered overhead armed while the other unarmed one crossed over the US ship's path 12 times to harass. Despite numerous warnings, the Fencers ignored the ship and provoked it. The ship did nothing in response. Fencers are being used along the border with Ukraine for possible invasion radar suppression and troop movement concealment through electronic means. The plane is far from obsolete although the design originates from the 1970s.