ers ▁that ▁eventually ▁exceed ed ▁sevent y ▁vessels . ▁Most ▁of ▁the ▁fleet ▁operated ▁under ▁flags ▁of ▁convenience ▁where ▁laws ▁and ▁reg ulations ▁are ▁more ▁la x ▁than ▁those ▁of ▁the ▁own ers ’ ▁country . ▁More ▁aust ere ▁reg ulations ▁in ▁countries ▁such ▁as ▁the ▁USA ▁which ▁afford ed ▁higher ▁w ages ▁and ▁safety ▁standards ▁allowed ▁access ▁to ▁domestic ▁routes ▁with ▁higher ▁fre ight ▁rates ▁but ▁at ▁far ▁greater ▁running ▁exp ense . ▁As ▁was ▁then ▁common ▁practice ▁in ▁international ▁sh ipping , ▁On ass is ' ▁fleet ▁had ▁mostly ▁Pan aman ian ▁and ▁Liber ian ▁flags ▁and ▁sa iled ▁tax - free ▁while ▁operating ▁at ▁low ▁cost . ▁This ▁and ▁his ▁ast ute ▁business ▁sense ▁helped ▁On ass is ▁ear n ▁hand some ▁prof its ▁in ▁the ▁highly ▁compet itive ▁sh ipping ▁market . ▁On ass is ▁made ▁large ▁prof its ▁when ▁the ▁Big ▁O il ▁companies ▁like ▁M obil , ▁So con y , ▁and ▁Tex aco ▁signed ▁long - term ▁contract s ▁known ▁as ▁time ▁char ters ▁at ▁fixed ▁prices ▁before ▁the ▁spot ▁market ▁fell . ▁ ▁The ▁high ▁profit ability ▁of ▁the ▁On ass is ▁fleet ▁has ▁been ▁attributed ▁in ▁large ▁part ▁to ▁his ▁dis reg ard ▁for ▁standards ▁that ▁normally ▁govern ▁international ▁sh ipping . ▁For ▁example , ▁after ▁his ▁Liber ian ▁registered ▁tank er ▁SS ▁Ar row ▁ran ▁a ground ▁and ▁sp illed ▁oil ▁into ▁Ch ed ab uct o ▁Bay , ▁Nova ▁Scot ia ▁in ▁ 1 9 7 0 , ▁still ▁the ▁most ▁significant