The high performance PARS operating system evolved from ACP (Airlines Control Program) to TPF (Transaction Processing Facility).
PARS (and IPARS) was extremely successful, and it massively improved and revolutionized the efficiency of airlines passenger operations and their profitability.
[2] In this context PARS was also used as a marketing name by TWA when selling their system to travel agencies.
Swiss International Air Lines and Brussels Airlines discontinued using PARS beginning of 2016.
IranAir, the Iranian National Airline, discontinued using IBM-ACP/IPARS at the beginning of 2000 due to Year 2000 (Y2K) problem.