Is it possible to detect a pitot static failure (blockage) of air data probe during flight and alert the pilot?
The crew checks the pitots and static ports before the flight to ensure they are in good condition and not blocked by objects or insects. Pitot tube (pitot-static) can be obstructed in-flight. Static ports are less affected.

Detecting a blocked pitot or static port: This is not done, but is possible (e.g. send some air from the back of the tube in a pitot, and see if it can exit the tube at a normal rate (which is dependent on several parameters).

Unblock a blocked pitot: In some cases yes:


Melt ice or snow by heating the tube in flight, but the tube may be frozen for a minute from time to time. Some pitots are not heated and must be deiced naturally, which will be longer (while cruising in -50°C air, friction prevents aircraft skin to be cold. Concorde skin was about 100°C, meaning air friction just increased its temperature by 150°C).
Drain water using drain holes in the pitot.


Redundancy for pitots: Yes, two or three exist on most airliners.

Alert for blocked pitot: Not a direct alert, since a blocked pitot is not detected, but air data processors compare the different pressure values received from the different pitots, and in case of significant difference alert the crew and disconnect the automated units relying on pitot pressure (like the autopilot).

A message is displayed to emphasize that airspeed is unreliable

Dangerous? Yes because if the unreliability of airspeed is not taken into account by the pilot, then stress and inappropriate actions can occur because the aircraft is apparently not reacting to attitude changes.

AF447 disaster is sadly a perfect demonstration of the stress that can be generated.

If the crew detects correctly the situation, then there is nothing special to do, they just need to continue (manual control) at the same altitude and with the same aircraft attitude until the speed becomes reliable again.