"forming up" with a car on the highway is much easier than forming up on another aircraft...especially one of a different type.
With a car, you're on a flat surface that eliminates several aspects: elevation, cross-wind/slipstream buffet (turbulence).
One the otherhand, at high-speeds on the highway, there is the risk of collision because of external conditions: animals crossing the roadway, oncoming traffic crossing over, debris on the roadway, etc. which you won't encounter in aircraft.
A Veyron can be easily paced by a Ferrari or a Hydndai or a VW bus, all depending on circumstances but dissimilar aircraft in formation presents special challenges, like in Heritage flights with a Spitfire, a P-40 and a modern combat jet for example. In like types (say like a formation of P-51Ds), they all have similar trim settings, throttle, pitch and so on, they can easily match the lead element and hold a nice formation.
But with a formation of different types, it takes different settings by each pilot to match the leader and bring the formation into order. Lots of work going on behind the scenes there!