Signing in, and deleting your account
There's no separate sign-up step. The first time you sign in, your account is created.
Ways to sign in: with a code sent to your email, with Apple, or with Google. Use the same method on the app and the website, and your saved flights and Pro follow you.
Signed in with Apple's "Hide my email"? Your account shows an address ending in @privaterelay.appleid.com. That's still your real account.
New phone, or Pro not showing? Sign in with the same account. If Pro still doesn't appear, tap Restore purchases in the app to re-link your Apple or Google subscription.
Deleting your account: you can do it yourself, in the app's Account tab or under Profile on aerolopa.com. Deleting your account doesn't cancel a subscription: cancel that in your phone's store settings first (see How do I cancel Pro or get a refund?).