You are not able to choose the box that you were on active duty unless you served for 90 days (consecutively) during the tax year. Active service Drills and AT do not count as active duty. Persons in the Reserve or National Guard are not full-time active duty military personnel, although they can be deployed at any time should the need arise.
See this link for similar answer https://ttlc.intuit.com/replies/5920985
So if I went through basic and straight to ait and was gone in total for about 18 weeks I check the box that says my wages are active duty pay?
If you in the National Guard you cannot claim active duty unless you were deployed. AIT does not count as active duty.
[Edited 01.14.18 9:07PM ET]
It doesn't count even though they pay active duty pay during that time period of your training?
Was this ever resolved? I have the same question. I was title 10 (which is active duty).. for 19 weeks straight.
Basic and AIT are paid as active duty hence considered active duty time, it counts.