Planes were temporarily grounded as the grenade, discovered by construction workers on the UK Power Networks site, was made safe by Explosive Ordnance Division operators.
A Gatwick Airport spokeswoman said: “A construction company working near the airport found what looked like a Second World War grenade when they were digging.
“British Transport Police cordoned off the area as a precaution and the Explosive Ordnance Division carried out a controlled explosion.
“It is now safe. Flights were not allowed to take off or land for about 10 to 15 minutes so there was a slight delay to services, but it was minimal.”
A British Transport Police spokesman said: “British Transport Police officers were called to Gatwick Airport railway station after the discovery of what is believed to be a WW2 grenade.
“The device was discovered on the lower ring road by a construction worker who was working on a piece of land there.”
