I don't think there are limits to how slow an aircraft can fly in any airspace.
200 knots
Sec. 91.117 - Aircraft speed.(a) Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.).(b) Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class C or Class D airspace area at an indicated airspeed of more than 200 knots (230 mph.). This paragraph (b) does not apply to any operations within a Class B airspace area. Such operations shall comply with paragraph (a) of this section.
The plane with the slowest max speed that was ever flown during WWI was the Bleriot XI, manufactured in france, and used primarly for Reconnaissance. It had a top speed of only 47 mph. The slowest American plane was the Aeromarine 40 Flying Boat Trainer Aircraft, with a top speed of 71 mph. The slowest aircraft actually used in battle was the Caproni Ca.1 Heavy Day Bomber, used in Italy, with a top speed of 75 mph. In America it was the Martin MB-1 / Glenn Martin Bomber Reconnaissance / Bomber Aircraft, with a top speed of 104 mph.
200 knots.
A rough estimate by me probably about 520-530 mph. The average cruising speed of a passenger jet, like the Boeing 737 is around 550 Miles per hour or Mach .75. This is not an exact number, and may vary depending on wind and weather conditions, altitude, aircraft weight, etc. depends on a lot of factors ie. aircraft weight, altitude and airspace.. if an aircraft is heavy, the pilot will try to be as safe as an airspeed as he can so probably he wont be going for the maximum speed. in the US the FAA rules state that the maximum speed below 10,000ft is 250 knots. typically on international airspace aircrafts travel from 250 knots to 320 kts cruising speed. but if you are in a controlled airspace, lets say when reaching US airspace, ATC might advise you to maintain a given speed, just like cars, airplanes also have a speed limit sometimes.
The slowest speed an object can move is zero.
the Elmatross is the slowest
Planets travel slowest at their aphelion – the point in their orbit farthest from the sun. This is when they are moving at their slowest speed due to the effect of gravity.
The slowest I've ever seen was 5 MPH, but this was on private property.
The speed of a planet revolving around the Sun is slowest at the aphelion, which is the point in its orbit farthest from the Sun.
FASTEST when dealing with speed
Monkeys