Texas State Sales and/or Use Tax on Glider bought out of state

I bought a glider in Canada 3 years ago, brought it back to Texas
where it is now hangared. It has been re-registered with new FAA N-
number etc.

I recently (after owning the plane for 3 years) received a letter from
the Texas Comptroller of Public Accounts saying I owe Texas sales tax
and/or Use Tax. They graciously say they are willing to forgive any
late payment penalty and interest if paid by May 30th.

Since I bought the plane out of state/country, do I still owe sale or
use tax?
Any insight (especially from a CPA) would be appreciated.