I worked at Eglin AFB and know a little about the GBU-43. It is satellite/GPS guided and can hit a target with extremely good accuracy.
The weapon is intended to have a high altitude release, allowing for greater stand-off range for the delivery vehicle. Following deployment from the aircraft via drogue parachute, the MOAB weapon is guided approximately 3 nautical miles through a GPS system (with inertial gyros for pitch and roll control), JDAM actuators, and is stabilized by series of fixed wings and grid fins. The weapon, which uses the aircraft’s GPS prior to launch, takes several seconds to reconnect to the GPS signal after it has been deployed, which is normal for GPS weapons.