Praise be to Allah.
The water that the passenger forgets or leaves behind in the airport may be with other luggage that belongs to the owner of that water, and his name appears on it, and has been officially received or checked in by the airline company. In that case, they should wait to see if the owner comes back to collect his belongings, including the water. If it is known that the owner will never return, or there is no chance that he will come back, or if the water will be spoiled or go off, then in that case it may be sold and the price given in charity on behalf of the owner of that luggage.
The company is only obliged to keep passengers’ belongings for the period stated in the contract with the traveller. Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was asked: There is a laundromat in which there are clothes that have been there for more than two months, and the owners are not known, even though one of the conditions on the invoice states that the laundromat is not responsible for clothes that the owners leave for more than two months. Does the owner of the laundromat have the right to take them, either to use them, sell them or give them in charity? If he takes them, then the owner asks for them after they have been disposed of, is he obliged to pay the value of the clothes or not?
If it was stipulated to the owner of the clothes that if he takes longer than two months to collect them, he forfeits his right to them because he is the one who delayed, then once the two months have ended, the owner of the laundromat may either give the clothes in charity if he finds someone who will accept them and wear them, or he may sell them and give their price in charity. But I think that he should wait for ten or fifteen days more after the two months have ended, because perhaps the owner was on his way, but his car broke down, or he fell sick, so it is better to wait.
End quote from Liqa’ al-Baab al-Maftooh (215/11).
He also said: If there was a specific time period agreed upon between them, then when that time ends, it is up to him whether he wants to give them in charity or sell them and give the price in charity.
But if there was no specific time period agreed upon between them, then it is not permissible to sell them after one or two months have passed; rather he should not sell them or dispose of them unless he has given up on the owner returning. If he has given up on that, then it is his choice, because he cannot store these garments or carpets indefinitely.
Liqa’ al-Baab al-Maftooh (215/19).
But if the water is not connected to other items (belongings) of some travellers, and the time for the flight’s departure has passed, there is no information on the bottle, and it has remained in the airport for so long that it is most likely that its owner has already departed and left it behind, or he has missed his flight, and it is not likely that he will return to the airport to ask for the water or look for it, then in that case there is nothing wrong with the pilots or other workers using it, because the ruling in this case is the ruling on lost property of insignificant value, or items that the owner left behind because he was no longer interested in it. This ruling states that it is permissible for the one who finds it to make use of it.
If the people in authority give it away to those who want it so that they can make use of it, whether they are workers or travellers, this is a good thing, if Allah wills.
And Allah knows best.