The RQ-170 Sentinel stealth drone which crashed/show down in the Iranian airspace was part of a joint CIA-US military spy mission and covert operation was considered by US military to retrieve or destroy the wreckage of the stealth drone.
Plans to retrieve or destroy the missing drone included options to send special operation team inside Iran or use air strike to destroy the wreckage of the drone. Both options were dropped because of the fear that it could result in a major clash with Iran.
It is believed that US stealth drone may have been already inside the Iranian airspace on a intelligence gathering mission for the CIA and US military forces. Iranian nuclear and missile programs has been the main focus of the western and Israeli intelligence agencies.