A fighter jet went down on Thursday in Idlib Province, according to witnesses cited by the Syrian Observatory for Human Rights, an activist group. Activists also said rebels had bombarded an air base in Idlib and may have seized part of it. Fighters claimed this week to have destroyed at least five helicopters in Idlib, and to have downed another over the Damascus suburbs. The government has disputed the claims. Rebels first said they had shot down a fighter jet on Aug. 13.