Methodist minister Rev Dan Woodhouse and Quaker activist Sam Walton were being held by Lancashire Police on suspicion of criminal damage following the incident this morning.
A statement issued on behalf of the pair said they had entered the site with the intention of disarming fighter jets.
The plan was to prevent the jets being delivered to the Saudi government which, they said, was due to take place in the new few weeks.
“Stopping or even delaying Saudi Arabia having more planes with which to bomb Yemen would save innocent lives and prevent war crimes,” Rev Woodhouse, who is a minister in Leeds, is quoted as saying.
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Mr Walton added: “We did not take these steps lightly, but we have no other option.”
Lancashire Police confirmed two people had been arrested on suspicion of criminal damage following an incident at the site and officers were investigating.
A spokeswoman for BAE Systems said: “The incident is now being investigated by Lancashire Police and we are assisting them with their inquiries.”A statement issued on behalf of the pair said they had entered the site with the intention of disarming fighter jets.