The location of the Mechanized Army First Division was to the south of the academy, roughly 10 hours of travel by car. If Melody wanted to go there in time through the land-route, then she'd have to depart before 10 p.m. assuming that she meets no delays along the way.
The current time was 6 a.m. and Melody was still within the academy's premises. Well, she never planned to go to the army through the land route, anyway.
"Sylveria to Control Tower, requesting permission to lift off."
She was instead already onboard her Doppel and ready to set off at any moment.
If she traveled through the air, riding her Doppel, then even if she didn't rush, she could still make it to where General Bethilda was in under 40 minutes. She should still have a lot of time to spare.
And she didn't even have to wait for long, as the permission already came a moment later.
{Control Tower to Sylveria, request confirmed. You are cleared to launch.}