Runway Incursions Runway incursions are defined as any threat of a collision on a runway between a plane and some other object, including another aircraft.

Since 1997 more than 1,300 incursions were reported, in 1997 alone 292, and in the year 2000 the number has raised to 429.

Incursions are categorized in different grades by the FAA. The most serious category is defined as a mistake so severe that a collision was "barely" avoided, the next category is defined as a situation, in which a significant potential for a crash existed, the third stage is a situation in which pilots had ample time and distance to avoid a collision, and the least serious situation is described as little or no chance of collision.

The number of serious incidents is nearly constant (21 in 1997; 20 in 2001), while the numbers raised particularly in the cases with lower risks.

The numbers include between general aviation and commercial airplanes. Despite the tremendous increase in flights, it is widely believed that runway incidents represent one of the biggest threats to safety. A recent study sponsored by the FAA predicts that runway collisions would be the No. 1 hazard in aviation over the next 20 years unless steps were taken to reduce the risk.

Several agencies, including the FAA, have started efforts to reduce the chances that airplanes could hit something or each other on the ground. It includes new markings at airports, studies about pilots and air traffic controllers failures and improved education for private pilots.