However, with increasing air traffic and the assignment of distinct flight levels to specific flights, airways, and directions of flight, it is no longer safe to climb continuously in this way, and so most flights compromise by climbing in distinct steps—a step climb—with air traffic control (ATC) approval, in order to ensure that the aircraft is always at an appropriate altitude for traffic control.
As air traffic rises and each flight receives unique flight levels, continuous ascent becomes unsafe. Consequently, most flights adopt a step climb method—ascending in discrete stages—with ATC authorization to maintain an appropriate altitude for ATC.