"The B-2 Spirit stealth bomber is the only aircraft in the U.S. Air Force inventory currently capable to operationally drop the massive 30,000-lb (14,000 kg) GBU-57 Massive Ordnance Penetrator (even though the testing of the MOP involved a B-52 back in 2009, the weapon’s intended platform is only the B-2).
The 14-ton GBU-57 is a 20-foot long GPS-guided bomb said to be able to penetrate 200 feet of concrete before exploding: for this reason it is considered the weapon of choice in case of attack on buried targets (such as the North Korean bunkers)," The Aviationist blog said.
The MOP was used in combat by the Air Force in Afghanistan, where it was dropped in the Nangarhar province in 2017, killing about 100 terrorists, hiding in an elaborate underground tunnel.