The demonstrators said Leonardo UK make components for F-35 combat aircraft, which they say are used by Israel.
They are calling on Leonardo UK to drop its F-35 contract with Lockheed Martin, which produces the aircraft.
Around 100 protesters, some holding Palestine flags, blockaded the entrance to the factory on Wednesday morning.
Andy, 30, who did not wish to give his surname, said: “We want to encourage workers of Leonardo to take action within their trade union to end this F-35 contract with Lockheed Martin, and amplify the voices of Palestine Action prisoners who have been on hunger strike in British prisons.”
Asleem, a 29-year-old health charity worker who also took part, said: “Officially there has been a ‘ceasefire’, but the indiscriminate killing and maiming has not ceased.”
Leonardo UK has been asked for comment.