United Airlines is set to open its biggest airport lounge this week, which it says is the largest in the Americas, as airlines continue to plow money into the facilities for high-spending customers.

The 54,000-square-foot lounge is opening Thursday at George Bush Intercontinental Airport's Terminal B in Houston, part of an overhaul of the airport that includes 22 gates for mainline aircraft.

The airport, with more than 500 departures a day, is United's main connecting hub for flights to and from Latin America.

The new club can seat 800 people and features an outdoor terrace for plane-spotting as well as two full-service bars and buffets.

The new lounge, part of United's $2.6 billion investment at the airport's Terminal B, shows how airlines are putting more money into larger spaces for premium-travel demand to attract the growing ranks of elite frequent flyers, co-branded credit card holders and customers just willing to spend more to fly.

American Airlines earlier this month said it is planning its largest-ever lounge at its Charlotte Douglas International Airport hub in North Carolina. Delta Air Lines has expanded both its popular Delta Sky Clubs and its top-tier Delta One Lounges.

Southwest Airlines is building its first-ever network of airport lounges, which are tied to its credit card partner, Chase. Last week, the carrier unveiled mock-ups of the lounges, which it is calling Icon. And JetBlue Airways opened lounges in New York and Boston in the past year.