Climate change activists are to stage an action week at Heathrow in protest at plans to expand the airport.
More than 2,000 climate change activists are expected
More than 2,000 people are expected to take part in a "camp-in" from 14 to 21 August at the west London airport.
Metropolitan Police Commissioner Sir Ian Blair has warned air travellers could face disruption.
The Camp For Climate Action protest coincides with one of the airport's busiest periods of the year, with 200,000 passengers every day.
In addition to setting up camp on a location which has yet to be disclosed, activists will hold workshops and debates.
"There will be a day of mass direct action aiming to disrupt the activities of the airport and the aviation industry," said organisers on their website.
"But in the interests of public safety there will be no attempt to blockade runways."
Sir Ian said although organisers were co-operating with police, they may not be aware of the plans of others.
"The vast majority of people coming to the camp will be activists with the most benevolent motives," he told a meeting of the Metropolitan Police Authority.
"But our intelligence shows that there are some people coming without benevolent motives and this has the potential to be a very disruptive event at Heathrow.
"We have been working our way through what we need and we will provide it... But it is likely there will be some disruption at Heathrow."
Heathrow operator BAA said it has applied for an injunction to protect the operation of the airport against any unlawful and disruptive activity.
A BAA spokesman said: "We respect people's right to protest within the bounds of the law and the airport by-laws and would invite protestors to similarly respect the rights of passengers travelling through Heathrow.
"We have proposed a number of sites at the airport for purposes of a lawful and peaceful protest, for discussion at the injunction hearing."