Does anyone know the rules for having a ticket endorsed?

My company travel people insist that they can only give me a NW ticket, even though NW offers only a lousy routing for this trip.

With NW I have to change planes and waste a whole lot of time. Meanwhile, Delta has a perfectly convenient direct flight to my final destination in Europe.

Any chance NW would endorse the ticket to Delta? Any tips on how to make this happen?

Thanks all