Badger, optimistically there may not be missing data after Feb 20. I read some old threads ("Delta Hiring News," p314, to be exact). It was Jan 11. There had been a lull in invites after the holidays and AeroCrewSolutions posted the following:

"If you should get an email in the next round of invites you can expect an interview date at the end of February or the beginning of March."

I got my invite two days later, Jan 13, but it was not for the end of Feb or early March. It was for a March 11th interview (the first interview on the spreadsheet after Feb 20). The gap between Feb 20 and Mar 11 could be real and not missing data.