Part of Amsterdam's Schiphol airport has been closed after a suspected World War II bomb was discovered, a spokeswoman said.
The departure hall serving most European destinations has been evacuated as a precautionary measure.
Delays are now affecting some departures and passengers are advised to check their flights before leaving for the airport.
A bomb disposal team is trying to establish whether the device is live.
The bomb was uncovered by workers digging near Pier C, which connects the main plaza with Departure Hall One, serving most destinations within Europe's 26-country passport-free Schengen zone.
"This will have a big impact. We can park planes somewhere else to some extent but at some point it will lead to cancellations or delays," the spokeswoman said earlier, according to Reuters news agency.
Schiphol was used as a military airfield by Nazi Germany during the 1939-45 war, and was often attacked by allied bombers, Dutch media said.
It is now one of Europe's busiest airports, handling some 48 million passengers every year.
Unexploded bombs dating back to the war are still frequently discovered in Europe.
A 550lb (250kg) American bomb was detonated by a bomb disposal team in the German city of Munich on Tuesday.
A 1.5-tonne mortar bomb probably fired by Nazi forces was also safely removed from the Polish capital, Warsaw.
And still they keep rising to the surface.
Some are born great, some achieve greatness and some have greatness thrust upon them.
The rest of us are a bit crap.