Answer: Yet in October 1936 Pan Am's "flying boat airliner" Clipper had flown passengers from San Francisco to Asia in six days, and the airline was taking steps for trans-Atlantic flights that would take 27 hours.
Explanation:
The Hindenburg was shown to be obsolete by the sentence above because of the time it took to complete a trans-Atlantix flight.
The new "flying boat airliner" was going to cross the Atlantic in 27 hours and the Hindenburg could only do it in 2 - 3 days which meant that it was up to 2 days slower.
People would prefer the faster vessel and move towards it with time which would eventually end the usage of the Hindenburg.