For an aircraft the size of an A380, to be as efficient as a smaller aircraft, it requires a much larger wingspan to avoid the induced drag penalty associated with smaller aspect ratio wings. The gatebox limit at airports prevents this increased wingspan resulting in much lower efficiency specifically for the A380.
A plane like a Boeing 747 uses approximately 1 gallon (about 4 liters) of fuel every second. Over the course of a 10-hour flight, it might burn 36,000 gallons (150,000 liters). The 747 burns approximately 5 gallons of fuel per mile (12 liters of fuel per kilometer).
That was one of the reasons Air France, the first European airline to fly the jet, decided to ditch A380 on August 5. The estimated cost of upgrading economy and business classes, at over $45 million (£37m), was just too much compared to investing into newer aircraft instead.
When all is said and done, the Airbus A380 needs 3,000 m (9,800 ft) of runway to take off fully-loaded, while the Boeing 747-8 requires 3,100 m (10,200 ft).
An A380 crosses the landing threshold at a docile 140 knots and touches down, depending on its landing weight, at a speed as slow as 130 knots, about the same touchdown speed of some corporate jets that weigh 1/50th as much as the world's biggest airliner.