In response to Beth Seaton's query -

The charter flight fails the test of "reasonableness" required by A-21.  If
a reasonable person would conclude that the traveler could or should have
used one of Beth's options, then it is unreasonable for the sponsor to
have to pay $500 for a charter.

It also fails Phil's Fifth Test of Allowability - I wouldn't want to explain
paying for a charter to the local newspaper or TV reporter!

Just some thoughts.

Phil Spina
Wright State University
xxxxxx@desire.wright.edu