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.
The craft did carry out a test flight in 2012, but next month's take-off will be the first under the hybrid aircraft's latest specifications. Airlander is the largest aircraft in the world, bigger even than the Airbus A380 - but would be dwarfed by the historic zeppelins developed in Germany during the 1930s.