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I wrote to United Airlines, asking them to re-consider gluten free meals
on their flights.  Got this reply...

Jan

Thank you for contacting us.  I know that when United fails to provide
the amenities you anticipate you may doubt our commitment to your
travel needs.  United offers twenty different meals to meet the
medical, religious, or dietary needs of customers.  These include
Kosher, diabetic, low cholesterol, and vegetarian and are available on
flights with scheduled meal or snack service.  As it is very difficult
for us to provide for the specific need of each customer, you may want
to consider carrying some small meal items with you to ensure that your
needs will be met on future flights.

Your comments have been given to our Onboard Service Department since
they continue to monitor customers' responses to changes.  Your
observations are important to us and will help us evaluate future meal
planning decisions.  We hope to have your understanding of this
important business decision.

Regards,
Dana