cal questions. where is the plane and what caused it to vanish? an official report on the disappearance of flight 370 reveals the pinger batteries on one of two black boxes expired long before. >> the family members -- >> reporter: lawyers representing 27 of the victims' families say that may have compromised the search. >> the balancettery pinger expired, it's another dagger in the heart of the families. >> reporter: the airline admits the maintenance oversight but denies it hampered the search because batteries on the other black box worked. the revelation is one detail in a newly released report which shows there was chaos and confusion in the hours after the pilot uttered his last words.