Two main theories have been postulated as to how gas could have leaked. Dr. Eckener believed a snapped bracing wire had torn a gas cell open (see below), while others suggest that a maneuvering or automatic gas valve was stuck open and gas from cell 4 leaked through. During the airship's first flight to Rio, a gas cell was nearly emptied when an automatic valve was stuck open, and gas had to be transferred from other cells to maintain an even keel. However, no other valve failures were reported during the ship's flight history, and on the final approach there was no indication in instruments that a valve had stuck open.