Present day auto-land systems are capable of landing an aircraft in zero/zero conditions. (That's zero ceiling and zero visibility.) However, most operators of US carriers rarely go to the expense of the additional training required to qualify crews to these minimums as zero/zero conditions are seldom encountered. Most only train crews down to minimums of 300' or 600' RVR. (Runway Visual Range is a specialized instrument measurement of lateral visibility as viewed along various portions of the runway.) Answer The aviation industry is developing a HUD (Head's Up Display) that will project Infra-Red imaging in front of the pilot that will greatly enhance his "vision" for adverse landing conditions, whether it is darkness, fog, etc. The cost of operating auto-land systems also includes equipment for the aircraft. So if an operator has a fleet of aircraft, this would require the operator to upgrade his fleet and train all of his crew so they could fly any aircraft in any condition as needed.
500 m
While it is definitely difficult to land a plane without spoilers or putting on the flaps, it is possible. The best scenario for a plane that is trying to land without these important instruments would be to try and obtain as much runway as possible.
Look at the plane ticket cost
As an inclined plane gets shorter, the angle gets steeper and the effort becomes greater.
In 2010, a volcanic eruption in Iceland brought much of Eoropean air travel to a halt. The increased levels of ash were bad for visibility nad plane engines.
It has to reenter the atmosphere and land like a plane.
9000 sqft
about an acre
It depends entirely on the type of aircraft and how it is flown.
Cessna is a small plane and it has less speed also. So 1 km is enough to land.
More effort, since the angle will need to be increased.
for every extra pound on a plane one extra foot of landing room is needed.