Bangladesh, Oct. 13 -- Flight MH181 was scheduled to depart at 11:55 pm on October 11 with 178 passengers. It eventually took off at 2:20 am with only 100 on board.

The airline did not officially explain the delay or the reduced passenger count. Sources, however, said the oxygen shortage was the reason some travelers were not allowed to board.

Aviation experts said a chemical reaction generates oxygen when overhead masks are pulled during an emergency.

Airlines declare certain seats inoperable if the chemical oxygen generator is not working, which could explain the denied boardings.

In a social media post, one passenger said travelers were stranded for more than six hours without water or information. The passenger said airline staff...