20thcentury 20thcenturyamericanhistory adventurers aeronauticalengineering aerospace aircraft airfreight airlineindustries airplanes allies- aviation aviationhistory aviationindustry biography businessfigures commercialaircr commercialaircraft commercialaviat commercialaviation commercialvessels conglomeratecorporations crudeoil cruisesandcruiseships defenseindustries destinations e energyindustries environmentalengineering flightinstruction general germany hazardouswastepolicies helicopters historicalbiography history labor maritimelaw merchantmarines militaryhistory miscellaneous navalhistory navaloperations navigation oceanography petroleum pictorial piloting pilots pollutants pollution sailing seafaringlife shippingindustries ships shipwrecks specificprofessions submarines travelreference underwaterexploration unitedstates unitedstateshistory waterpollution worldtravel worldwari worldwarii