During last night season finale "My name is Oliver Queen" we see Oliver and Nyssa jump into the cockpit of the plane and Oliver manages to crash-land the plane without injury.
But the question Is where did Oliver learn the skills to pilot a plane? So far none of the flashbacks have showed where Oliver learned this skill. At the end of the flashbacks in season 3 finale we see Oliver boarding a ship "Triton's Daughter" which is owned by the Wallace Shipping Co. straight out of Coast City.
This is where the theory kicks in. DC fans know this city because it's the home of none other than Hal Jordan aka Green Lantern. Hal Jordan is a test pilot for Coast City Ferris Air. In the Flash episode "Rogue Air" we see Captain Cold and Flash waiting for the plane to arrive at the Ferris Air Field. Captain Cold then says "Wasn't this place shut down?" Barry tells him, "It did. One of their test pilots went missing."'
We know that pilot was of course Hal Jordan. So if Oliver boarded the "Triton's Daughter" which is straight out of Coast City could we be getting flashbacks dealing with Hal? Could we get Oliver crossing paths with Hal? Did Oliver learn to pilot a plane from Hal? It seems more and more likely. I think it would make pretty awesome flashbacks to see two future major DC heroes interacting. In the comics Green Arrow and Lantern teamed up a lot. So it wouldn't be too far fetched. What better pilot than Hal Jordan to teach Oliver to pilot a plane.