Airspeed is not something you can see. It has to be measured, and the pitot tube does the job. The small probe sticks into the airflow and captures ram air pressure. Compare that pressure to the static pressure from a nearby port, and the difference gives you airspeed.

Pitot tubes are heated because ice can block them. A blocked tube gives false readings, which has caused serious accidents. Air France 447 and Birgenair 301 both involved pitot icing or blockage that misled the crew.

Where pitot tubes sit

• Nose of the fuselage on many aircraft
• Wing leading edges on others
• Multiple tubes for redundancy
• Separate probes for different systems

Ground crews cover the tubes when an aircraft is parked, and pilots verify covers are removed before flight. It sounds trivial until a forgotten cover leads to a wrong airspeed indication on takeoff.