To book a flight I recently created a British Airways account; soon after an email arrived asking me to setup two-factor authentication. After initiated the process I got interrupted by something and when I returned the session expired; when I called BA to send me another email for this I was told they couldn't.
I thought I would just delete the account and started all over again; this actually required me to fill up an online request and took a few days for the account to be deleted. While waiting I decided to just create a new account using another email address, thinking I could change it to my preferred email address later. Turned out that change also required me to fill up another online form.
I have accounts with half a dozen airlines (US, Asia and Europe), BA is the only one that still has such outdated IT from the '90s :(