Update 11.40am: Seven people have been arrested following an airport protest - though passengers remain grounded, with disruptions to flights in and out.
The activists were from the nine-strong Black Lives Matter group who stormed the runway at London City Airport shortly before 6am.
The Metropolitan Police said the seven have been held on suspicion of aggravated trespass, being unlawfully air-side and breaching airport by-laws after eyewitness reports that the group swam across the Thames to gain access to the Royal Docks site before locking themselves to a tripod frame.
Two people remain locked together on the runway.
Several emergency service vehicles were parked on the runway as attempts were made to clear the protesters.
A man in black, who had attached himself to the top of a wooden structure, was surrounded by police officers and a set of aircraft steps were wheeled up to him in an apparent bid to get him down.
Police boats could also be seen circling the dock surrounding the runway.
Having attached a helmet to the man, police removed him from the top of the structure and on to the plane steps.
After sitting briefly on the platform with a rope around him, he was taken down.
A police van was seen driving down the runway, away from the scene.
Passenger Casey Collins said customers were unaware of the protest until after 8am, and assumed the delays were related to IT glitches at Heathrow and Gatwick.
The freelance management consultant from Devizes in Wiltshire was supposed to be on a 7.35am flight to Luxembourg.
He said: "The board was saying all BA flights were on hold, and that there would be updates at 8am, so we thought it was a continuation of the problems at Heathrow and Gatwick with BA.
"We then realised that things were more serious because all flights were being affected.
"It started to get a little bit out of control in terms of staff letting people know.
"We didn't know why we weren't being called to board, it just said the next information would be at 8am and that people were being encouraged to queue up at the info desk.
"But the problem was that there were only two or three staff there and the queue was about 150 yards long, so it was impossible.
"Pretty soon they realised they would have to do a queue-walk to inform everyone. People were behaving themselves, they know it was not the airport's fault, but for a time it was a bit chaotic."
He said passengers were offered refunds for cancelled flights, while delayed passengers were also given refreshment vouchers.
Fellow passenger Chanel de Kock said she was stuck for three-and-a-half hours upon arrival in London.
She said: "The flight information boards had no information, and there wasn't any information given by the airport, this was really frustrating for passengers. Then standing in queues for hours to 'check out', then only given a pamphlet
to call the airline.
"I wish the airport would tighten their security as it's a bit worrying that people can access the runway so easily in the current state of our times, and also that the airport will be better at giving information to people at the airport.
"It was absolute chaos and really badly handled by what I thought was my favourite airport."
Earlier: Passengers at London City Airport have been grounded after protesters stormed the runway.
Flights were disrupted at the airport, in the Royal Docks area of the capital, after activists apparently in support of the Black Lives Matter movement made their way air-side at around 5.40am on Tuesday.
An airport spokesman said: "We're currently experiencing disruption to all flights due to protesters at the airport. Police are currently on the scene."
It is the latest demonstration involving anti-racism activists, who brought traffic to a standstill outside Heathrow Airport - and carried out similar protests in cities around the country - in a co-ordinated day of action last month.
The campaigners, whose international movement was set up following the murder of black teenager Trayvon Martin in Florida four years ago, said Tuesday's action was taken "in order to highlight the UK's environmental impact on the lives of black people locally and globally".
New post: "
Protesters storm the runway at London City Airport bringing flights to a standstill and stranding tho… https://t.co/YEY1OBnpg8— Lee Levy - Dubai Life Coach (@thekingleelevy) September 6, 2016
In a statement, the protest group's UK division cited expansion plans at the airport as the cause of their action.
They said: "Recently London City Airport was given approval to expand its capacity, a move that consigns the local community in Newham to further deterioration of their environment. The average salary of a London City Airport user is €136,000 and 63% of them work in business, finance or other business services.
"It is an airport designed for the wealthy. At the same time 40% of Newham's population struggle to survive on £20,000 or less. When black people in Britain are 28% more likely to be exposed to air pollution than their white counterparts, we know that environmental inequality is a racist crisis."