They could argue that it's just the celebrity form of car pooling/sharing, but we're all just assuming Miley Cyrus and Kellan Lutz are dating 'cause they were spotted emerging from the same private jet recently. They just flew into Miami after a jaunt to the Bahamas, as you do at this time of year. Perhaps Miley saw him trying to hitch a lift roadside and offered him a ride.
They went to great pains not to be photographed together, leaving the jet separately, and so on, the usual kind of thing when one of the party has an impending movie release that needs promoting (Kellan is starring in Hercules, which just happens to be bringing itself to a cinema near you shortly).
Although, perhaps they left separately as Lutz wasn't arsed waiting for Miley to totter down the airplane steps in those crazy ass shoes.