I've confirmed that the $20 and $50 promo codes are reusable. Waiting on someone to post a 75 or 100 code to see if they are reusable. Since that is 50 each way(book separately) you get a 100 off roundtrip.

It looks like they are following same pattern as June. 8 digit codes reusable. 10 digit(high value) codes, one time use.