Here are some examples of Captain Marvel only being able to leap and not fly. First we have a panel from Whiz Comics #2 - Cap's origin! Notice that he leaps across a mighty chasm!
In Whiz Comics #4, Captain Marvel is chasing Dr. Sivana and Beautia who are trying to escape. He's not flying after them, but running! When the bridge is destroyed, he doesn't fly, he makes a giant leap.
Here are the panels from Whiz Comics #5 where we first see Captain Marvel flying!
Captain Marvel's powers and abilities grew from his first comic as his character became more settled. This is exactly what happened to other comic book characters as well. I'm glad Captain Marvel was given the ability to fly - and soon he was able to time travel by flight! When did Captain Marvel first fly? I believe it was in the pages of Whiz Comics #5!!