You are flying a VFR cross-country leg of 100 nautical miles using dead reckoning navigation with no wind forecast. Your planned true airspeed is 110 knots, for an estimated time en route of 55 minutes. After 40 minutes airborne, using pilotage you estimate you have 20 nautical miles remaining to your destination. Pressure altitude is 8,000 feet, and outside air temperature is +25°C. Which factor most likely explains why you are ahead of schedule?

(Refer to the provided figure.) The airport elevation shown on the sectional chart excerpt is 2,000 feet. The current altimeter setting is 30.00 in. Hg, and the outside air temperature (OAT) is 20°C. The approximate density altitude is