American has given its bottom-tier Gold elite members two extra months of complimentary “Main Cabin Extra” extra legroom seating at time of booking (through February 28), will give Gold elites continued free access to those seats on day of departure starting March 1, and will offer the ability for them to purchase extra legroom seats at 50% off in advance at that time as well.

When American first announced the introduction of Main Cabin Extra, Gold members were only going to get the seats for free through December 31, 2013. So this is a two month extension of the free benefit.

What’s more, American unlike United (which only gives their first-tier elites access to these seats at check-in, and don’t give their Premiers a discount on advance purchase) offers equivalent oneworld partner airline elites the same access to their extra legroom coach seats that they do to their own elite members.

AAdvantage® Executive Platinum and AAdvantage Platinum members and their oneworld equivalents*, as well as customers who purchase a full-fare Main Cabin ticket, receive complimentary access to Main Cabin Extra seats. This benefit was offered to Gold status members to celebrate the launch of our new seating product and was set to expire on December 31, 2013. We have good news — we’ve extended it through February 28, 2014!

We know the extra legroom is important to you when traveling in the Main Cabin, so starting March 1, 2014, we are pleased to offer Gold status members and oneworld Ruby members^ two ways to access Main Cabin Extra seats:

• Purchase Main Cabin Extra for 50% off
  
• Enjoy complimentary access to Main Cabin Extra within 24 hours of departure (if seats are available)

Hat tip to Lucky, who also explains Delta’s policy:

Delta’s Economy Comfort policy is far too complex to summarize, but they also offer complimentary Economy Comfort within 24 hours of departure on North American/Caribbean flights to their Tin Silver Medallions (the rough equivalent to AAdvantage Gold and United Premier Silver). Silver Medallions can also purchase Economy Comfort in advance at 50% off for North American itineraries, or 25% off for all other international itineraries.

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