You should deduct the expense as a charitable deduction in the year you paid for the airline ticket, unless you will be reimbursed for the expense by the non-profit.  

Please explain your difficulty in entering this expense in TurboTax.

The date of travel was 01/14 – 1/17/2016. In the "Brief description of travel" box I enter "travel to non-profit foundation board meeting." In "Date of travel" box I enter "01/14/2016." In "Other travel costs - total" box I enter the amount of the ticket. In "Brief description of other travel costs" box I enter "airfare paid in 2015 for travel to this meeting in 2016." TurboTax comes back with the following error message "We Need More Information.....You either left the date field blank or entered an invalid date on the previous screen. Go back and double-check the date of travel field. Possible errors may include: etc, etc."

I see the problem.  Instead of entering the plane ticket as a travel expense, enter a cash donation for the cost of the ticket  and delete the travel information.  Please keep in mind that if you don't make the trip for some reason, you'll need to amend your return and delete the donation.

Thanks, Richard.