I've noticed that blocked pitot tubes, or ones where the cover or tape wasn't removed after cleaning the jet, have had several serious consequences. When the pre-flight walk around is done, is it SOP that an individual checks the pitot tubes for blockages? It said that sometimes Maintenace forgets to remove the covers or the tape. I'm surprised there isn't a warning system that alerts the pilots if they are covered or blocked since they are crucial for flight safety. What have they done to prevent these types of accidents from occurring again? (ie. Air Peru 757, Air France, Malasiya Air, etc. years ago.) Is it SOP for commercial pilots to call out 'live airspeed' upon take off, so they know that the pitot tubes are working? Surprised that their blockages or being covered or taped over, wasn't caught prior to take off. The exception being them icing over temporarily in flight, which caused a major problem for a flight, as they hadn't read the NOTAM regarding what to do. It was on Air Disasters.