Eight protesters who caused hundreds of flights to be cancelled or delayed at Stansted Airport have admitted aggravated trespass.
The seven men and one woman, aged between 18 and 29, appeared before Harlow Magistrates' Court in Essex.
The protest on 8 December, organised by Plane Stupid, aimed to highlight the impact of aviation on the environment.
They were released on bail and will be sentenced on 7 January. They are the first of 49 people to appear in court.
Appearing in court were Joe Ryle, 18, of Hornsey, London; Joseph Booth, 20, of Roehampton; Mark Haworth, 22, of Manchester; David Hood, 29, of Machynlleth, Powys; Guy Mitchell, 20, of west London; Oliver Robinson, 19, of Muswell Hill, London; Yamuna Soto, 22, of Roehampton; and Jonathan Leighton, 19, of Oxford.
They said of their decision to disrupt the airport: "We did so with heavy hearts, knowing it would disrupt passengers, because we knew the consequences of this action couldn't be worse than the consequences of inaction.
"If our government continues to champion the growth of carbon emissions millions of lives will be destroyed."
Prosecutors said the demonstration caused the cancellation of 57 Ryanair flights which were due to carry nearly 7,000 passengers.
A further 52,000 passengers also had their travel plans disrupted as more flights were delayed, the court heard.
Anthea Soares, prosecuting, said damage estimated at £3,000 was caused to perimeter fencing at the airport after the protesters cut through and barricaded themselves inside the perimeter.
The other people charged will appear before magistrates next year.
Ben Newton, representing seven of the defendants, said: "We are dealing with conscientious, educated, hardworking members of society, all of whom are of good character."
Magistrates' chairman Russell Pearson released them on conditional bail banning them from entering airports unless flying as a "bona fide" passenger.