the documentation that contains all the reasoning and arguments used to demonstrate that the performance objectives (and performance targets) will be met.
A performance case can be seen as the combination of the various cases that together address and balance all areas in which the ATM community has expectations, e.g. the safety case, together with the business case, together with the environment case.
ICAO (2009), doc. 9883, Manual on Global Performance of the Air Navigation System
Lexicon Release 2015.2