Online guides: If you lose your luggage
Baggage delivery is one of the most common problems in airports, especially in large ones like Rome Fiumicino and Milan Malpensa. Your bags may be delayed or lost. However, Consumer Protection Association highlights that half-an-hour delay is enough to ask for compensation, but you need to report the loss of your luggage first.
First of all, the traveller has to go to the "Lost and found" Office at the airport to report damaged or lost luggage; you'll have to show your ticket, your boarding card and baggage receipt, and fill an ad hoc form.
If you are away from home, after 24 hours most airlines have to make sure that you have the necessities you need to survive while your bag is being located. If luggage is not returned within 48 hours you can ask for a monetary compensation. You have to produce your claim to the national airline company within 3 days in case of damage and within 14 days for luggage loss. For long range flights, it's 7 or 21 days respectively according to the cause.