A taxi guys picked up a passenger at the Burj Al Arab who wanted to go the Dubai airport. Due to traffic, the average speed was rather low and the trip to the airport took 80 minutes. At the airport, the taxi picked up another passenger who, coincidently, wanted to go back to the Burj Al Arab. The taxi driver took the same route as before, had the same average speed, but this time the trip took 1 hour and 20 minutes.
Can you explain why?