For those of you interested in purchasing miles, this opens up a temporary means of doing so that's both cheaper than UA's direct purchase program, and with a higher annual cap:

- With UA direct purchase, you can buy up to 60,000 miles for yourself per calendar year. The cost, including taxes and transaction fees, is anywhere between $0.0328/mile and $0.673/mile, depending on quantity.

- With Amex MR, you can purchase up to 500,000 miles per year, as long as you immediately transfer them to a partner program. The cost, including tax, is $0.0252 - $0.0256 per mile, depending on the amount (no transaction fee).

So, if you have some way to redeem high-value UA awards, you can buy up to a half-million miles through this method between now and Sept 30 for around $0.025/mile.

Separate from points purchase, you could do a points advance, and borrow against your next year's Amex spending at no cost and transfer those to CO and then UA.