max air will not start up

See: Try Disk Utility here > Resolve startup issues and perform disk maintenance with Disk Utility and fsck

Tell a bit more about the macbookair:

model or year number,

what OSX do you have on it?

If you have OS Lion or later, you can use DiskUtility from the Restore Partition probably:

Start up while holding CMD+R, (slow start), then choose DiskUtility to repair disk and repair permissions.

Lex