They were arrested after cutting through Stansted Airport's perimeter fence and locking themselves together around a deportation plane.
The Boeing 767 jet targeted by the group, operated by Titan Airways, was chartered by the Home Office to transport people from UK detention centres for repatriation to Nigeria, Ghana and Sierra Leone in March 2017.
Rt Rev Stephen Cottrell attended several of the court sessions as the campaigners defended their actions.
Following the guilty verdicts, Judith Reed, of the Crown Prosecution Service said: "These people placed themselves, the flight crew, airport personnel and police at serious risk of injury or even death due to their actions on the airfield.
"The CPS worked with the police to build a strong case which reflected the criminality of the defendants' actions, regardless of their motivation."
During the trial several of the protesters sought sanctuary at Chelmsford Cathedral.
Defending their actions, Bishop Stephen said: "Deportation charter flights are a brutal way of forcing people out of the UK: Mothers, fathers, siblings and neighbours; people who are part of our communities, are being snatched away and forced onto charter flights in the middle of the night.
"Many of these people have lived in our communities for decades and have no current connections with the places to which they are being deported; including areas where the rule of law is, to say the least, fragile.
"Peace makers are often initially perceived as trouble makers.
"I am grateful that the Stansted 15 have reminded us of our most fundamental commitments to speak and act for those without a voice.
"Yes, it may have looked like they were making trouble. They weren't. They were making peace.
"As they await sentencing, they intend to appeal their convictions. I earnestly look forward to the day of their speedy exoneration. Please join me in praying for them."
The defendants, aged between 27 and 44, will be sentenced on February 4 at Chelmsford Crown Court.
Their charge carries a maximum penalty of life imprisonment.
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