Pakistan International Airlines has confirmed loss of contact with an ATR 42 operating domestic flight PK661 from Chitral to Islamabad.
A statement posted on Twitter by airline spokesman Danyal Gilani indicates that the turboprop was carrying "around 40 persons".
It adds: "All resources are being mobilised to locate the aircraft. Media will be kept informed as situation develops."
Media reports have suggested there were 42 passengers and five crew aboard the aircraft. No further details are immediately available.
Flight Fleets Analyzer lists six ATR 42-500s in PIA's inventory.