London City Airport has been closed after a 500kg World War Two bomb was found nearby in the River Thames.
The airport will be shut all day and all flights cancelled, affecting up to 16,000 passengers, a spokeswoman said.
The bomb was found at George V Dock on Sunday during pre-planned work at the east London airport, police said.
Families in the area have been evacuated with the exclusion zone set to be widened when specialists begin removing the device.
The airport was shut at 22:00 GMT on Sunday. The Met Police said it was working with the Royal Navy to remove the bomb.
A statement issued by the Met said: “The timing of removal is dependant on the tides, however, at this stage we estimate that the removal of the device from location will be completed by tomorrow morning.”
According to the airport’s website, a total of 261 arrivals and departures had been scheduled for Monday.
“All flights today are cancelled but some airlines have moved their flights to other airports – CityJet to Southend and Alitalia to Stansted”, the airport said.
Passengers have been told not to travel to the airport as the terminal is closed and to contact their airline.
The device is a German 500kg bomb, measuring approximately 1.5m (59in), according to specialist officers and the Royal Navy, Newham Council said.
Robert Sinclair, CEO of the airport, apologised and said: “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.”
Members of airport staff are on Hartmann Road, the main route to the airport, to help redirect people.
Airlines using London City Airport include British Airways, Flybe, CityJet, KLM and Lufthansa, with flights to domestic and European city destinations.
Police said a 214-metre exclusion zone had been set up and properties inside were evacuated.
A rest centre has been opened by Newham Council to provide bedding and refreshments for families who have been affected.
One passenger arriving at the airport had been hoping to board a flight to Milan.
“We don’t know what to do”, the passenger told BBC London.
“We’re going back to the city to get more information as there’s nobody here to help. We’ll have to call our airline and hopefully we’ll arrive back in Milan soon.”
Streets affected include Holt Road, Leonard Street, Lord Street, Newland Street, Tate Road, Muir Street and Kennard Street.
When work begins to lift and remove the device, the exclusion zone will be extended to 250m and more properties will need to be evacuated, the council said.
“While we endeavour to progress the operation as quickly as possible and minimise disruption, it is important that all of the necessary steps and precautions are taken to ensure it is dealt with safely,” the Met said.
Police said a number of road cordons were in place and advised motorists to avoid the area.
Docklands Light Railway services between the airport and Woolwich Arsenal have also been suspended.
Between September 1940 and May 1941, the Germans dropped about 24,000 tonnes of explosives on London – but 10% of all bombs that dropped did not detonate, according to historians.