Interview question

Operations has decided to redefine the company's on-time performance (OTP) KPI: from "share of operated flights arriving within 15 minutes of schedule, measured at wheels-on" to "share of scheduled flights arriving within 10 minutes, measured at the gate (cancelled flights count as not on time)". On a synthetic 2,000-flight sample the headline falls from 95.3% to 81.2%. Bonuses and an investor target are tied to the old number. You own the KPI. How do you explain and roll out the change so that nobody concludes that performance collapsed, and how do you give a defensible account of "why 14 points"?