London City Airport was shut on Sunday after a World War II bomb was found in the nearby River Thames.
The airport will remain closed all day Monday, seeing all flights cancelled and around 16,000 passengers affected, according to a spokeswoman.
The bomb was discovered by construction workers in the George V Dock at 5 am local time on Sunday, Met Police said.
Workers were conducting pre-planned work at the airport when it was discovered and police were called as well as the Royal Navy, who confirmed the nature of the bomb.
"Following the discovery of a World War II ordnance in King George V Dock as part of planned development works, a 214-metre exclusion zone has been implemented," the airport said in a statement. "As a result, London City Airport is currently closed."
"The airport is cooperating fully with the Met Police, Royal Navy and London Borough of Newham," it wrote.
Operations are ongoing to remove the device.
A 214m exclusion was implemented in the area and residents living inside the boundary were moved out of their properties to temporary accommodation, provided by Newham Council, said police.
They also said a number of road cordons had been put in place and advised motorists to avoid the area.
Services on the Docklands Light Railway between the airport and Woolwich Arsenal were also suspended.
Robert Sinclair, CEO of the airport, apologised in a statement on Twitter saying: "I recognise this is causing inconvenience for our passengers and in particular some of our local residents.
"The airport is cooperating fully with the Met Police and Royal Navy and working hard to safely remove the device and resolve the situation as quickly as possible."
He also advised passengers with flights on Monday not to travel to the airport but to contact their airline.
Located in the borough of Newham, east London, companies operating out of the airport include Alitalia, British Airways, CityJet, Flybe, KLM, Lufthansa, Luxair and SkyWork Airlines.
The British Army tweeted that bomb disposal experts from the army and the navy would work together to safely dispose of the unexploded bomb.