Hmmm it has happened (quite famoulsy) at Qantas before.
It's easy to work out -- if you steal from your airline, be prepared to lose your job --- its as simple as that. There is no excuse for it.
It used to be common practice to take things off the aircraft, but no longer. I would never 'dob-in' someone for it. But if you decide to steal supplies off the aircraft, then you have to face the reality that if you are caught, you will be fired and have a criminal conviction. Its not a hard concept.
Never forget folks, that when you are in a slip port, you are still on company time. Therefore you are subject to rules of the company. At Qantas, this means that they can search your hotel room -- as the contract states that they can search you , or your property (cars etc) whilst you are on company property, or propety contracted to the company. This includes hotel rooms, as the company pays for them.
Its not worth it.