An unexploded bomb from WWII was discovered in the River Thames early last Sunday, which led authorities to cancel all flights Monday out of neighboring London City Airport. Because bombs are not only bad, they are also highly inconvenient.

The bomb was discovered during some pre-planned work for the airport. The Royal Navy and specialists alike confirmed that it was a German, 500-kg (1,100-pound) device with a fuse coming out of it, reported . Until the device was lifted and removed, nobody was permitted to start work around it. I’m not what you might call a “bomb” “expert,” but let’s declare this one a “smart” “move.”

On Sunday evening, the Royal Navy and the police evacuated people within about 700 feet of the bomb, reported .

There were 261 arrivals and departures scheduled for the airport on Monday, noted the . Up to 16,000 passengers were affected. I suspect, however, that “bomb threat” is a reason for delay that goes down far more easily than “airport personnel incompetence.”

By Monday evening, the authorities had the bomb from the area. Thankfully, no one was injured.

The reason for the evacuation, in addition to the immediate danger posed by a normal bomb, is rooted in the nature of a WWII Nazi bomb. The Nazis dropped all kinds of bombs during the war, but some were booby trapped to only go off when someone tried to defuse them. And visually, there was nothing differentiating these from unexploded duds. From the :

But according to a spokesman for the RLC regiment’s EOD division, high explosive, air-delivered German bombs are the most dangerous World War II items it has to deal with. Not only are they in a sensitive state – having already been deployed, armed and damaged by the impact with the ground – but they are fitted with a variety of different fuses, some designed to detonate immediately, others which featured some form of time-delay and some which were booby trapped, specially designed to kill EOD operators.

Of course, finding old and unexploded WWII-era bombs in London really isn’t all that unusual. German planes dropped almost 30,000 bombs on the city over the course of three months during the Blitz, reported.

And it’s not just London either. Each year, over 2,000 tons of unexploded bombs are found in Germany, despite the war ending some 70 years ago, reports .

And, as it turns out, leftover war bombs have a nasty habit of turning up where people least want them to. There was that time some 1,200 residents were evacuated in London when a construction crew unearthed a . And that other time when an was discovered in Savannah, Georgia.

I think the rule of thumb here is that if you live anywhere where there’s been a war, which is pretty much everywhere, be mindful when you dig.