Originally Posted by Bucking Bar

Another take from the site that leaked the A350 order before Delta even told it's BOD:

April 12, 2017, © Leeham Co.: Delta Air Lines today said on its earnings call that it is reviewing its wide-body order with Airbus.
At face value, the Delta statement might seem alarming. But as so often becomes the case, the “review” may not be what it seems.
Summary

• There is more activity about fleet requirements than simply “reviewing” the wide-body orders.
• Delta’s preparing to issue an RFP for single-aisle Airbus A321neos and/or Boeing 737-9/10s.
• Boeing hopes Delta will be a launch customer for the MAX 10.
• The NMA/MOM aircraft could be involved.