[Scythian]

.The World's largest airport area 776 km2 is bigger than whole of Singapore 710 km2

"King Fahd International is also the largest airport in the world by area, with the area of the airport property being an approximate 776 square kilometers (300 mi2),"

Note
Singapore island area 710km2

[Scythian]

"Top 10 Largest Airports in the World by Land Area (in square miles):

King Fahd International (DMM) — Dammam, Saudi Arabia — 776 km2 (299.61 mi2)
Denver International (DEN) — Denver, CO United States — 135.7 km2 (53.09 mi2)
Dallas/Fort Worth International (DFW) — Dallas, TX United States — 69.6 km2 (26.88 mi2)
Orlando International (MCO) — Orlando, FL United States — 53.8 km2 (20.78 mi2)
Washington Dulles International (IAD) — Washington D.C., United States — 48.6 km2 (18.75 mi2)
Beijing Daxing International (PKX) — Beijing, China — 46.6 km2 (18 mi2)
George Bush Intercontinental (IAH) — Houston, TX United States — 44.5 km2 (17.19 mi2)
Shanghai Pudong International (PVG) — Shanghai, China — 39.9 km2 (15.4 mi2)
Cairo International (CAI) — Cairo, Egypt — 36.3 km2 (14 mi2)
Suvarnabhumi International (BKK) — Bangkok, Thailand — 32.4 km2 (12.51 mi2)""

Singapore is extremely tiny by comparison 

[klat]

But in terms of passengers per sq km, Changi is the highest.