From:
Airman spots aircraft fuel leak at 35,000 feet
I like the part: "Sergeant Bachleda said the captain and the crew were trying to figure out how the aircraft was losing 6,000 pounds of fuel an hour"
So did the flight crew think that passengers were drinking it?
BTW: the airline was
United.
Lets not forget the Air Transit A-330 in route to Europe which developed a fuel leak from inproper maintence. When the systems notified the pilots of the fuel unbalance they thought that the systems was at error.
They ran out of fuel and that A-330 became a glider at 35000' and 170 miles from an energency dead stick landing in the Azores.