Depends on type, the fastest would probably be military and go several times the speed of sound. Commercial planes cruise at around Mach .81, with red lines close to the speed of sound Mach .90 or so. For comparison a Cessna 172 red line is 163 Kts.
It depends on what aircraft you are talking about. An F-16A can go 1,500 mph.
Fast enough to do the job. The actual maximum speed of all stealth aircraft is classified. Like any aircraft, the speed will depend on many factors.
The maximum height at which a passenger aircraft can fly is 40000 feet.
The maximum height flown by an aircraft is 37650m(123524ft). The aircraft is Mig-25 Foxbat.
370 knots
Usually walking speed, -4-5 mph.
Ground speed is the speed the aircraft has compared to the ground. This is usually different from air speed, which is the aircraft's speed compared to the surrounding air. Thus an aircraft with 400 kph air speed and 50 kph headwind has a ground speed of 350 kph. For fun: with light aircraft with very low stall speeds it's possible to fly backwards (compared to the ground) if they fly into a headwind that's stronger than their lowest stall speed. I.e. their ground speed is negative.
It depends what aircraft and what speed you are going
Charles Yeager was the first person ever to pilot an aircraft beyond the speed of sound.
The Air Force still hasn't said how fast an SR-71 will go. We do know they'll fly 1800 mph without much stress.
5
That is it's maximum speed. Different for every aircraft.
It depends on which aircraft is being used.