Machines use X-rays to inspect luggage.
All baggage headed for the cargo hold of an airplane is inspected at this level. Operator then either clears the bags or sends them to Level 3. Bags rejected by Levels 1 and 2 are examined at Level 3 for traces of explosives. Any bag failing all three levels of inspection is reconciled with the passenger and cleared before it goes on the plane. Some of the tools being developed or currently available for use at airports to scan checked baggage.