Clark wasn't able to fly yet? He couldn't be out of college yet then, from what Diana recalled. Clark had said he hadn't developed flight until he'd moved to Metropolis. "No, you misunderstand," Diana said, quietly, still waiting on Clark to hopefully open the door. "He wanted you to learn...he just wanted to teach you himself, but the rest of the JLA pointed out that as Superman, he was too busy and you needed a more permanent teacher. That's why he didn't like it."
She glanced at Kara, hearing the faint derision in her tone. "Your cousin didn't master flight until he was out of college, if I remember correctly, but trust me. His powers have only improved with time. And yes, you still had a lot to learn. But eventually you did join a team." Diana would have liked to have Kara with her on the JLA team, but she'd preferred to go with the Legion, and later the Titans. She sensed that right now was not the time to go into Kara's latest misadventures. The girl had no idea.