Germany's Hannover Airport is in lockdown after a possible explosive was found in the parcel centre.
Officers were alerted after employees at a UPS depot in Langenhagen found the item.
Planes that were due to land are currently in a holding pattern.
Passenger Adam Nicholls said: "Just landed back at Heathrow Airport after Hanover Airport got shut down due to a suspect package, after we had circled over head for 30 minutes.
"Great start to the trip."