At indoc, we were told an LOR type document is not necessary for internal. On the 6 friends that got the invite I just typed 2-3 simple sentences in the email and attached their latest resume. We were told the email alone would guarantee that the record was scored. We were also told the airline apps LORs don't get read until pulled for an interview. I've read contradictory info here so not sure what is really the process. I guess that your app may get points for having an LOR on file from a delta pilot but it's content may not matter until interview. Again I am just guessing here.

I always review all my internal recs resumes and delta application before sending email to hiring team. Wait time from sending to invite has been across the spectrum from 1-day to over 2-3 months. Most recent in Jan took less than a week. Good luck to all.