While airline stocks have not recovered to pre-pandemic levels, passengers have returned in record-breaking numbers. The year 2023 was Denver International Airport’s busiest on record, with an estimated 78 million passengers. United Airlines is Denver’s biggest operator. It recently invested nearly $1 billion in Denver to add more gates, flights and destinations, and opened the largest lounge in its network. The airline wants to grow to 650 flights a day before 2030. CNBC got a behind-the-scenes look at United’s Denver operations.