  The mixing of three active neutrino flavors is parameterized by the unitary
PMNS matrix. If there are more than three neutrino flavors and if the extra
generations are heavy isosinglets, the effective $3\times 3$ mixing matrix for
the three active neutrinos will be non-unitary. We have analyzed the latest T2K
and \nova data with the hypothesis of non-unitary mixing of the active
neutrinos. We found that the 2019 NO$\nu$A data slightly (at $\sim 1\, \sigma$
C.L.) prefer the non-unitary mixing over unitary mixing. In fact, allowing the
non-unitary mixing brings the \nova best-fit point in the
$\sin^2\theta_{23}-\delta_{CP}$ plane closer to the T2K best-fit point. The
2019 T2K data, on the other hand, cannot rule out any of the two mixing
schemes. A combined analysis of the NO$\nu$A and T2K 2019 data prefers the
non-unitary mixing at $1\, \sigma$ C.L.. We derive constraints on the
non-unitary mixing parameters using the best-fit to the combined NO$\nu$A and
T2K data. These constraints are weaker than previously found. The latest 2020
data from both the experiments prefer non-unitarity over unitary mixing at $1\,
\sigma$ C.L. The combined analysis preferes non-unitarity at $2\, \sigma$ C.L.
The stronger tension, which exists between the latest 2020 data of the two
experiments, also gets reduced with non-unitary analysis.
