This is a follow-up to my previous question:

[How does this IMU work and how to convert its output into meaningful information?](https://aviation.stackexchange.com/questions/45039/how-does-this-imu-work-and-how-to-convert-its-output-into-meaningful-information)

for which many people asserted that I need a pitot tube and a static port in order to calculate airspeed and pressure altitude respectively, and errors will build up if I just integrate the accelerometer values from the IMU.

I'd like to know whether it is possible to **measure airspeed without a pitot tube, accurately**? Is there any electronic sensor that can be used for this purpose?

Also are there any airplanes around the world, Airliners, GA, Military, or even Experimental, that operate without any pitot tubes?