Originally Posted by MSPeconomist

The issue is that your employer bought YOU a D1 ticket for business purposes. It's fraud to give it to a spouse and technically doing so creates a tax liability for you and a reporting requirement for your company. In some organizations this could be grounds for termination.

Originally Posted by flyerCO

It can be fraud since the cost of the D1 ticket is a tax deductible business expense when paid for the employee to travel. If the wife instead flies in D1 then only the coach fare is a tax deductible business expense. The D1 fare then becomes for the employee taxable benefit from the company. It would need to be reported out on their W2 as earnings and taxes withheld. Failing to report this thus does become fraud not only against the company, but against the IRS.