Dear

Thank you for giving  [name of agency]  the opportunity
to make your travel arrangements for your recent trip to
[destination]

We hope that you were pleased with the air travel and the
hotel accommodations that we arranged for you.  We encourage
your comments, insofar as that is the best means that we
have for learning first hand if the representations of
quality that are made to us are accurate.

We will look forward to hearing from you and hope that you
will afford us the opportunity to help you plan your next
vacation or business trip.  Thank you.