Hello Walter,
That's why, for example, airplanes have things that must be removed before flight attached to big red flags that hang outside. You don't really want to find out after you're airborne that your pitot tubes still have the dust cap on!
Or even better: http://www.aircraftspruce.com/catalog/graphics/10-02000.jpgthe local airport added these to it's rentals after a few aborted takeoffs (from bugs in the tubes).
