Prosecutor Alexandre Gauthier said Piazza could face up to 10 years in prison and that the investigation is ongoing. He didn't rule out the possibility of additional charges.
"There may be more serious accusations, but it's hard to tell what's going to come out of the investigation right now," Gauthier said.
Piazza, a stocky man with a clean-shaven face, wore a black suit and dress shirt in his brief appearance at the Montreal courthouse. He addressed the court in English.
Piazza is set to appear again Tuesday for a bail hearing.
Police said they searched the suspect's apartment and car in a residential area near the airport Sunday evening after the package was spotted earlier in the day.
They seized some documents but Ian Lafreniere, a Montreal police spokesman, said they have found "nothing obvious" so far.
Members of the city's SWAT team were called in and authorities set up a security perimeter spanning several city blocks during the search. About 20 residents were temporarily evacuated from their homes.
The package was spotted at a security checkpoint in the U.S. departures area early Sunday morning. Lafreniere describe the seized items as "different parts of a potential device."
"To make that a little clearer, let's say you are trying to do a bomb inside the luggage, but one thing was missing: no explosives, but it was different parts of a dangerous device," Lafreniere said.
Piazza was detained, everyone on the flight was questioned, and luggage was searched as a precaution, Lafreniere said.
Flights destined for the United States were delayed for several hours on Sunday morning but an airport spokeswoman said flight operations had resumed by early in the afternoon.
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Associated Press writer Rob Gillies in Toronto contributed to this report.
