At collision prevention, the similarities between the two crafts end. Air Traffic Control is not at all involved with schedules and on time performance of airlines, nor with the scheduling of maintenance of facilities with the movement of traffic. When flight 802 leaves the gate, it takes its turn in line regardless of whether it is late or even possibly more important than the traffic ahead. It might even be held to leave behind a private or commuter plane with no regard for its scheduled leaving time because of dangers inherent to small planes taking off immediately behind large jet aircraft. Arriving traffic takes its turn in line as it enters the airspace surrounding an airport and flight 802 although delayed and arriving late, may circle, or hold behind other traffic that arrived ahead even though that traffic may be arriving ahead of schedule. Only a fuel shortage or mechanical failure will expedite the arrival of flight 802. On the contrary, while preventing collisions between trains in the limited 2-dimensional space, train dispatchers must constantly consider the schedules of all trains involved and arrange track maintenance and meets between opposing trains in a manner that on time trains remain on time and late trains make up time. Train dispatchers must also, while handling traffic, maintain reports of delays that occur to trains.
Train dispatchers directly and individually supervise not only each train movement, but also each track maintenance operation, deciding when maintenance will be allowed to begin and when each maintenance worker must be clear of the track. Every instruction is issued after consideration of schedule and performance. Every report of the location of a train initiates new calculations of where trains are as opposed to where they should be. Every request by maintenance forces to work on the track or the signal system likewise initiates a new recalculation.