After Darica and Duke left Monroe Village, they didn't head straight to the airport but went to Duke's apartment.
There were a few things that Duke wanted to pick from there. Also, he wanted to leave the car as he couldn't go with it to the airport when Darica was going to be spending a few weeks with him in Sonis.
He felt that leaving the car at his apartment was much safer than leaving it to the airport staff.
The two did exactly that and once they were done, they took an Uber to the airport.
When they reached the airport, Duke, who wanted to give his girlfriend the best treatment, didn't purchase any economy class tickets but opted for first class.
He wanted to give Darica the best first experience of flying, using the best class and taking the best class for that felt authentic.
Besides, he had the money to do that, so why save when he could earn brownie points from her by doing that?