This offer been available for awhile and is targeted. You should be able to find it when you login to your americanexpress.com account. Here are the terms of the online version, which ends soon. The email version could be different.
Details
Get a 1X $400 statement credit by using your enrolled Card to spend $2000+ on airfare only online at qantas.com by 4/14/16. Purchase must be made on Qantas’ US website in USD. Flight must originate in US. Not valid on vacation packages. See terms.
Terms
Valid online only. Flight must originate in US. Valid only on purchases of airfare made at Qantas’ US website. Purchases must be made in US Dollars. Not valid on purchases made by phone or at physical locations including, but not limited to the Qantas shop, the Qantas store and Qantas clubs and lounges. Offer not valid on purchases made in flight. Offer not valid for any purchases of a vacation package or through a third party (including resellers and online marketplaces). Qantas freight airfare not included. Offer not valid on any purchases made by using Membership Rewards® points from American Express. Excludes Corporate Cards and all prepaid Card products (other than registered American Express Serve® and BlueBird® Cards). Enrollment limited. Must add offer to Card and use same Card to redeem. Only US-issued American Express® Cards are eligible for this offer. Limit 1 statement credit per American Express Card across all American Express offer channels. Statement credit will appear on your billing statement within 90 days after 4/14/2016, provided that American Express receives information from the merchant about your qualifying purchase. Note that American Express may not receive information about your qualifying purchase from merchant until all items from your qualifying purchase have been provided/shipped by merchant. Statement credit may be reversed if qualifying purchase is returned/cancelled. If American Express does not receive information that identifies your transaction as qualifying for the offer, you will not receive the statement credit. For example, your transaction will not qualify if it is not made directly with the merchant. In addition, in most cases, you will not receive the statement credit if your transaction is made with an electronic wallet or through a third party or if the merchant uses a mobile or wireless card reader to process it. By adding an offer to a Card, you agree that American Express may send you communications about the offer. POID: C9FE:0001