On-time Performance (OTP) is the governing performance metric for ground handlers and airlines alike. It underpins SLAs and a swing of just a few per cent can be the difference between a star station and an also ran. But, is everyone measuring the same thing when it comes to this fundamental KPI? When should the turnaround officially start and finish and do nuances in the way some airlines define ground time inadvertently set us up collision course with carriers? This session will take a more detailed look at aviation’s dominant performance metric and discuss how standardising it definition could provide universal benefits.