Campaign group End Deportations said eight activists had locked themselves to a tripod to stop a "mass deportation charter flight" from the Essex airport to Nigeria and Ghana.
Stansted Airport said police had contained the incident but flights were suspended while they carried out further inspections.
The protest was on a "remote part of the airfield" not by the main passenger terminal, a spokesman for the airport said.
He added: "Flights are currently suspended but there have not been any affected at the moment as it is a quiet period.
"The police have contained whatever the protest is and they are just carrying out further inspections. We hope to resume operations fairly shortly."