Merz also believes that intensified security cooperation between participating countries would thwart criminals seeking to take advantage of relaxed border controls.
Swiss border police arrested 67 people for extradition, had found 112 missing persons and conducted 1,059 fruitful searches from the time Switzerland signed up to the Schengen Information system (SIS) criminal database in November last year to the end of February.
"At first glance, Schengen may seem like an attempt to square the wheel: greater security through greater freedom," Merz said in a speech. "Upon closer inspection, however, this apparent contradiction is resolved."
Airports were the last border points to complete preparations for Schengen because of the large infrastructure changes required to fulfil the new conditions.
Redevelopment at Switzerland's largest airport, Zurich, cost around SFr300 million ($262 million) with costs being passed on to airport users in the shape of a SFr4 charge for every passenger.
swissinfo, Matthew Allen in Zurich