The Flying Ford Anglia flew through the sky alongside the flying motorcycle. Although they had won the battle, and it had been an almost complete victory, Moody did not look particularly happy.
To Moody, Arthur's actions were a textbook case of disregarding organization and discipline, failing to follow the plan laid out in advance.
Even if breaking the rules this time had produced good results, saving Mundungus Fletcher and helping them repel the Death Eaters to prevent further casualties, that did not mean it was right.
They had been lucky this time; no one more dangerous had been there. But what if their luck had been worse? What if Voldemort had come in person? Arthur would have been the culprit who delivered Harry straight into Voldemort's hands.
Arthur knew all this too, so he awkwardly chose to ignore Moody—after all, he should have taken Harry away directly, rather than bringing him into the battle.
Now that he had come to his senses, he knew he had been reckless. Flying a car for the first time had been so exciting, and with Harry asking him to come to the rescue and his two sons egging him on, he had actually done it.
As it happened, George and Fred should not have been there at all. The brothers had eaten Animal Crackers and hidden inside the car. By the time they returned to their original forms, Arthur had almost reached Privet Drive.
Sirius came over as well—he was very interested in the Flying Ford Anglia. After all, he had already made a flying motorcycle, so seeing Arthur driving a flying car naturally made him itch to try it.
If they had not needed to take Harry back first, he would have loved to discuss Muggle inventions with Arthur right then and there.