Sulfate-reducing microorganisms are responsible for the sulfurous odors of salt marshes and mud flats. Much of the hydrogen sulfide will react with metal ions in the water to produce metal sulfides. These metal sulfides, such as ferrous sulfide (FeS), are insoluble and often black or brown, leading to the dark color of sludge.
The largest aircraft used for a scheduled domestic service in the USA that is a DOMESTIC route only, is the Boeing 777, though the most common is a Boeing 757 and 767. Some airlines use larger aircraft on domestic legs on an international flight throughout the USA, which do include the 747, however some airlines don't have a license to carry domestic passengers on those routes.
If we continue to measure by maximum takeoff weight, the next largest plane in the world would be either the related An-124 transport or the Boeing 747 airliner. Both aircraft are quoted with a maximum weight around 900,000 lb (405,000 kg).