At the player's maximum height, their velocity is 0. Recall that
[tex]{v_f}^2-{v_i}^2=2a\Delta y[/tex]
which tells us the player's initial velocity [tex]v_i[/tex] is
[tex]0^2-{v_i}^2=-2g(0.65\,\mathrm m)\implies v_i=3.6\dfrac{\rm m}{\rm s}[/tex]
The player's height at time [tex]t[/tex] is given by
[tex]y=v_it-\dfrac g2t^2[/tex]
so we find their airtime to be
[tex]0.65\,\mathrm m=\left(3.6\dfrac{\rm m}{\rm s}\right)t-\dfrac g2t^2\implies t=0.36\,\mathrm s[/tex]
