I went through the steps to erase my old MacBook Air and am not sure if it is completely erased. I launched it and get a blinking ? and a note on the bottom of the screen "support.apple.com/mac/startup.
Any advice on what I do from here to ensure all my data is erased?
MacBook Air 13″, macOS 10.14
This screen is shown when your Mac doesn't have an operating system to boot up...so, yes, it's been erased.
If you're going to gift your old MacBook to someone, you might want to load the operating system on it, though.
Here's an Apple Support article on how to do that: If your Mac starts up to a question mark - Apple Support
Hope this helps.
Erasing old MacBook
