For AA, call them up - they have a status challenge program. $120 to sign up for challenge to Gold (equivalent to US Silver) and $240 for Platinum (equivalent to US Gold). You have to fly 5000 EQPoints for Gold, 10K for Platinum in 90 days. Keep in mind that's POINTS and discounted economy fares are only 0.5EQP per mile. So on deep discount fares, you'll have to fly 20,000 miles for Platinum.

You can only start a challenge on the 1st or 16th of a month.

As for DL -- https://www.delta.com/planning_reser...atus_match.jsp