We have been told by DoE that agreements between US-flag air carriers and
foreign carriers are acceptable as long as the ticket clarifies the carrier
is US.  The difficulty is when (1) the ticket agent does not ascertain the
traveler has a "US carrier" ticket when actually ticketing (though you
were verbally assured), or (2) when the traveler changes plans and the
carrier cannot accommodate the change with a US carrier ticket.  These
agreements are common practice now.

  Sue Brightman, Administrator, High Energy Physics
  University of Rochester