It is axiomatic that a reasonable search is not to be determined by any fixed formula but is to be resolved according to the facts of each case. Given the circumstances obtaining here, we find the search conducted by the airport authorities reasonable and, therefore, not violative of his constitutional rights. Hence, when the search of the box of piaya revealed several marijuana fruiting tops, appellant is deemed to have been caught in flagrante delicto, justifying his arrest even without a warrant under Section 5(a), Rule 113 of the Rules of Criminal Procedure. The packs of marijuana obtained in the course of such valid search are thus admissible as evidence against appellant.130 (Citations omitted)

The reason behind it is that there is a reasonable reduced expectation of privacy when coming into airports or ports of travel:

Persons may lose the protection of the search and seizure clause by exposure of their persons or property to the public in a manner reflecting a lack of subjective expectation of privacy, which expectation society is prepared to recognize as reasonable. Such recognition is implicit in airport security procedures. With increased concern over airplane hijacking and terrorism has come increased security at the nation’s airports. Passengers attempting to board an aircraft routinely pass through metal detectors; their carry-on baggage as well as checked luggage are routinely subjected to x-ray scans. Should these procedures suggest the presence of suspicious objects, physical searches are conducted to determine what the objects are. There is little question that such searches are reasonable, given their minimal intrusiveness, the gravity of the safety interests involved, and the reduced privacy expectations associated with airline travel. Indeed, travelers are often notified through airport public address systems, signs and notices in their airline tickets that they are subject to search and, if any prohibited materials or substances are found, such would be subject to seizure. These announcements place passengers on notice that ordinary constitutional protections against warrantless searches and seizures do not apply to routine airport procedures.131 (Emphasis supplied, citations omitted)

This rationale was reiterated more recently in Sales v. People.132 This court in Sales upheld the validity of the search conducted as part of the routine security check at the old Manila Domestic Airport—now Terminal 1 of the Ninoy Aquino International Airport.133

Port authorities were acting within their duties and functions when it used x-ray scanning machines for inspection of passengers’ bags.134 When the results of the x-ray scan revealed the existence of firearms in the bag, the port authorities had probable cause to conduct a search of petitioner’s bag. Notably, petitioner did not contest the results of the x-ray scan.

IV