ORD is the busiest airport in the US

ORD of course stands for Chicago O'Hare International Airport.  It surpasses Atlanta's Hartsfield Jackson Atlanta International Airport  (ATL).  ORD had 903,000 arrivals and departures in 2018.

POP for Gregorio Luperón International Airport.

Want to learn more about these 3 digit airport codes?  Visit https://www.world-airport-codes.com/.