A 41-year-old man from France is being questioned after "what appears to be a firearm" was discovered in a bin at Gatwick airport, Sussex Police said.
The airport's North Terminal was evacuated following a subsequent security alert, but has now been re-opened.
A French man has appeared in court charged with possessing an air rifle and a knife following an evacuation at Gatwick Airport.
Jerome Chauris, 41, from Vendome in central France, was arrested on Saturday after allegedly walked into the airport's North Terminal carrying the weapons.
Wearing a white striped shirt and his black shoulder-length hair swept back, Chauris identified himself with the help of an interpreter.
During the hearing he wept and made several comments in French.
The incident, which took place at around 9.30am on Saturday, sent parts of the airport into lockdown and caused significant disruption to travellers.
Check-in was closed for six hours and is said to have cost airlines and passengers an estimated £1.2m.
The court heard how thousands of passengers and airport staff were evacuated from the terminal's 'landside' concourse, the area before luggage screening and security checks open to the public.
Officers from the Explosive Ordnance Disposal team then moved into the departure hall and carried out a small controlled explosion on a suspicious package.
Mr Chauris, of no fixed address, was remanded in custody to appear before Lewes Crown Court on 14 December.
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