In 1999, Skytrax established the World Airline and Airport Star Rating Programme; a leading international rating system that classifies airlines and airports by the quality of product and staff service standards. They award Airline Star Ratings (from 1 to 5 stars, 5 being the best) based on detailed, professional analysis of an airline’s quality standards via their audit office. This rating covers airport services at the airline’s hub, and onboard standards across all applicable cabin / aircraft types. They also provide Airport Star Ratings which includes a quality assessment across all customer-facing items of product and service that an airport provides. In both cases, the focus is on cleanliness and has been done in the past through visual inspections. Once COVID-19 hit, Skytrax needed a new way to verify "clean".